Journals >Chinese Optics Letters
Contents
2021
Volume: 19 Issue 9
19 Article(s)
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Reviews
Instrumentation, Measurement, and Optical Sensing
Review of femtosecond laser fabricated optical fiber high temperature sensors [Invited]
Dong-Ning Wang
The femtosecond laser has been an efficient tool for optical fiber high temperature sensor construction. Here, we review the progress of optical fiber high temperature sensors based on femtosecond laser fabricated fiber gratings and various types of fiber in-line interferometers in silica fibers and sapphire fibers.The femtosecond laser has been an efficient tool for optical fiber high temperature sensor construction. Here, we review the progress of optical fiber high temperature sensors based on femtosecond laser fabricated fiber gratings and various types of fiber in-line interferometers in silica fibers and sapphire fibers..
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 091204 (2021)
Integrated Optics
Mode division multiplexing: from photonic integration to optical fiber transmission [Invited] | On the Cover
Jiangbing Du, Weihong Shen, Jiacheng Liu, Yufeng Chen, Xinyi Chen, and Zuyuan He
To overcome the capacity crunch of optical communications based on the traditional single-mode fiber (SMF), different modes in a few-mode fiber (FMF) can be employed for mode division multiplexing (MDM). MDM can also be extended to photonic integration for obtaining improved density and efficiency, as well as interconnection capacity. Therefore, MDM becomes the most promising method for maintaining the trend of “Moore’s law” in photonic integration and optical fiber transmission. In this tutorial, we provide a review of MDM works and cutting-edge progresses from photonic integration to optical fiber transmission, including our recent works of MDM low-noise amplification, FMF fiber design, MDM Si photonic devices, and so on. Research and application challenges of MDM for optical communications regarding long-haul transmission and short reach interconnection are discussed as well. The content is expected to be of important value for both academic researchers and industrial engineers during the development of next-generation optical communication systems, from photonic chips to fiber links.To overcome the capacity crunch of optical communications based on the traditional single-mode fiber (SMF), different modes in a few-mode fiber (FMF) can be employed for mode division multiplexing (MDM). MDM can also be extended to photonic integration for obtaining improved density and efficiency, as well as interconnection capacity. Therefore, MDM becomes the most promising method for maintaining the trend of “Moore’s law” in photonic integration and optical fiber transmission. In this tutorial, we provide a review of MDM works and cutting-edge progresses from photonic integration to optical fiber transmission, including our recent works of MDM low-noise amplification, FMF fiber design, MDM Si photonic devices, and so on. Research and application challenges of MDM for optical communications regarding long-haul transmission and short reach interconnection are discussed as well. The content is expected to be of important value for both academic researchers and industrial engineers during the development of next-generation optical communication systems, from photonic chips to fiber links..
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 091301 (2021)
Lasers, Optical Amplifiers, and Laser Optics
Rare-earth ions-doped mid-infrared (2.7–3 µm) bulk lasers: a review [Invited] | Editors' Pick
Hongkun Nie, Feifei Wang, Junting Liu, Kejian Yang, Baitao Zhang, and Jingliang He
Mid-infrared (MIR) laser sources operating in the 2.7–3 µm spectral region have attracted extensive attention for many applications due to the unique features of locating at the atmospheric transparency window, corresponding to the “characteristic fingerprint” spectra of several gas molecules, and strong absorption of water. Over the past two decades, significant developments have been achieved in 2.7–3 µm MIR lasers benefiting from the sustainable innovations in laser technology and the great progress in material science. Here, we mainly summarize and review the recent progress of MIR bulk laser sources based on the rare-earth ions-doped crystals in the 2.7–3 µm spectral region, including Er3+-, Ho3+-, and Dy3+-doped crystalline lasers. The outlooks and challenges for future development of rare-earth-doped MIR bulk lasers are also discussed.Mid-infrared (MIR) laser sources operating in the 2.7–3 µm spectral region have attracted extensive attention for many applications due to the unique features of locating at the atmospheric transparency window, corresponding to the “characteristic fingerprint” spectra of several gas molecules, and strong absorption of water. Over the past two decades, significant developments have been achieved in 2.7–3 µm MIR lasers benefiting from the sustainable innovations in laser technology and the great progress in material science. Here, we mainly summarize and review the recent progress of MIR bulk laser sources based on the rare-earth ions-doped crystals in the 2.7–3 µm spectral region, including
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 091407 (2021)
Research Articles
Fiber Optics and Optical Communications
Compact vector twist sensor using a small period long period fiber grating inscribed with femtosecond laser
Fangcheng Shen, Xuewen Shu, Kaiming Zhou, Haiming Jiang, Hongyan Xia, Kang Xie, and Lin Zhang
We propose and demonstrate a sensitive vector twist sensor based on a small period long period fiber grating (SP-LPFG) fabricated with a femtosecond (fs) laser. The fabricated SP-LPFG is compact in size (2.8 mm) and shows strong polarization dependent peaks in its transmission spectrum due to the vectorial behavior of high-order cladding modes. Twist sensing is realized by monitoring the polarization dependent peaks, since the polarization of input light changes with fiber twist. The proposed sensor can be interrogated by the peak intensity and wavelength, with high twist sensitivity that reaches 0.257 dB/deg and 0.115 nm/deg, respectively.We propose and demonstrate a sensitive vector twist sensor based on a small period long period fiber grating (SP-LPFG) fabricated with a femtosecond (fs) laser. The fabricated SP-LPFG is compact in size (2.8 mm) and shows strong polarization dependent peaks in its transmission spectrum due to the vectorial behavior of high-order cladding modes. Twist sensing is realized by monitoring the polarization dependent peaks, since the polarization of input light changes with fiber twist. The proposed sensor can be interrogated by the peak intensity and wavelength, with high twist sensitivity that reaches 0.257 dB/deg and 0.115 nm/deg, respectively..
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 090601 (2021)
Infrared and Terahertz Photonics
Liquid crystal integrated metamaterial for multi-band terahertz linear polarization conversion
Shitong Xu, Fei Fan, Hongzhong Cao, Yinghua Wang, and Shengjiang Chang
We experimentally investigate the linear polarization conversion for terahertz (THz) waves in liquid crystal (LC) integrated metamaterials, which consist of an LC layer sandwiched by two orthogonally arranged sub-wavelength metal gratings. A Fabry–Perot-like cavity is well constructed by the front and rear gratings, and it shows a strong local resonance mechanism, which greatly enhances the polarization conversion efficiency. Most importantly, the Fabry–Perot-like resonance can be actively tuned by modulating the refractive index of the middle LC layer under the external field. As a result, the integrated metamaterial achieves multi-band tunable linear polarization conversion.We experimentally investigate the linear polarization conversion for terahertz (THz) waves in liquid crystal (LC) integrated metamaterials, which consist of an LC layer sandwiched by two orthogonally arranged sub-wavelength metal gratings. A Fabry–Perot-like cavity is well constructed by the front and rear gratings, and it shows a strong local resonance mechanism, which greatly enhances the polarization conversion efficiency. Most importantly, the Fabry–Perot-like resonance can be actively tuned by modulating the refractive index of the middle LC layer under the external field. As a result, the integrated metamaterial achieves multi-band tunable linear polarization conversion..
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 093701 (2021)
Instrumentation, Measurement, and Optical Sensing
High sensitivity cascaded helical-core fiber SPR sensors
Xianbin Wang, Hongchang Deng, and Libo Yuan
The distributed optical fiber surface plasmon resonance (SPR) sensors have attracted wide attention in biosensing and chemical sensing applications. However, due to the limitation of their sensing structure, it is difficult to adjust their resonant wavelength and sensitivity. Here, novel and flexible cascaded helical-core fiber (HCF) SPR sensors are proposed theoretically and experimentally for distributed sensing applications. It is shown that the resonant wavelength and sensitivity of the sensors can be conveniently controlled by adjusting the twist pitch of the helical core. A high sensitivity of 11,180 nm/RIU for refractive-index measurement ranging from 1.355 to 1.365 is realized experimentally when the twist pitch of the helical core is 1.5 mm. It is worth noting that the sensitivity can be further improved by reducing the twist pitch. For example, the sensitivity of the sensor with a twist pitch of 1.4 mm can theoretically exceed 20,000 nm/RIU. This work opens up a new way to implement multi-parameter or distributed measurement, especially to establish sensing networks integrated in a single-core fiber or a multi-core fiber.The distributed optical fiber surface plasmon resonance (SPR) sensors have attracted wide attention in biosensing and chemical sensing applications. However, due to the limitation of their sensing structure, it is difficult to adjust their resonant wavelength and sensitivity. Here, novel and flexible cascaded helical-core fiber (HCF) SPR sensors are proposed theoretically and experimentally for distributed sensing applications. It is shown that the resonant wavelength and sensitivity of the sensors can be conveniently controlled by adjusting the twist pitch of the helical core. A high sensitivity of 11,180 nm/RIU for refractive-index measurement ranging from 1.355 to 1.365 is realized experimentally when the twist pitch of the helical core is 1.5 mm. It is worth noting that the sensitivity can be further improved by reducing the twist pitch. For example, the sensitivity of the sensor with a twist pitch of 1.4 mm can theoretically exceed 20,000 nm/RIU. This work opens up a new way to implement multi-parameter or distributed measurement, especially to establish sensing networks integrated in a single-core fiber or a multi-core fiber..
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 091201 (2021)
Reconstruction of Fabry–Perot cavity interferometer nanometer micro-displacement based on Hilbert transform
Hongwei Liang, Yu Sun, Zhen Huang, Chunlei Jiang, Zihua Zhang, and Lingling Kan
A novel reconstruction method of nanometer micro-displacement of Fabry–Perot (F-P) interference is proposed in this study. Hilbert transforms are performed for F-P interference fringes, and the obtained signal performs tangent operation with the original signal. Finally, the validity of the proposed algorithm and the structure are verified by simulation and several experimental measurements for vibration. Results from the experiments show that the maximum relative error is 4.9%.A novel reconstruction method of nanometer micro-displacement of Fabry–Perot (F-P) interference is proposed in this study. Hilbert transforms are performed for F-P interference fringes, and the obtained signal performs tangent operation with the original signal. Finally, the validity of the proposed algorithm and the structure are verified by simulation and several experimental measurements for vibration. Results from the experiments show that the maximum relative error is 4.9%..
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 091202 (2021)
Random Bragg-grating-based wavelength-tunable random fiber laser with a full-open cavity
Bing Lü, Wentao Zhang, Wenzhu Huang, and Fang Li
A full-open-cavity wavelength-tunable random fiber laser (WT-RFL) with compact structure and hundreds of picometers tuning range is proposed and demonstrated. A π fiber Bragg grating (FBG) is used in the WT-RFL as a filter to select lasing wavelengths. The two random Bragg grating arrays (RBGAs) and a section of high gain erbium-doped fiber result in a low lasing threshold and high stability. A numerical model to analyze the tunable characteristics is developed. The results show that the laser threshold is 22 mW, and the maximum peak-power fluctuation is 0.55 dB. To the best of our knowledge, it is the first time that a compact and full-open-cavity WT-RFL with two RBGAs and a π-FBG is proposed.A full-open-cavity wavelength-tunable random fiber laser (WT-RFL) with compact structure and hundreds of picometers tuning range is proposed and demonstrated. A
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 091203 (2021)
Lasers, Optical Amplifiers, and Laser Optics
High power Yb-fiber laser amplifier based on nonlinear chirped-pulse amplification at a repetition rate of 1 MHz
Renchong Lü, Hao Teng, Jiangfeng Zhu, Yang Yu, Wei Liu, Guoqing Chang, and Zhiyi Wei
We report a high power fiber amplifier based on nonlinear chirped-pulse amplification (NCPA). To manage the nonlinearity, pulse shaping is introduced by self-phase modulation in the fiber stretcher with the help of spectral filtering. The third-order dispersion is compensated for by the nonlinear phase shift in the NCPA. With optimization, the system can output 382 fs pulse duration with 20 W average power at 1 MHz repetition rate. The long-term average power fluctuation is measured to be 0.5% in 24 h, and the beam quality factor (M2) is 1.25.We report a high power fiber amplifier based on nonlinear chirped-pulse amplification (NCPA). To manage the nonlinearity, pulse shaping is introduced by self-phase modulation in the fiber stretcher with the help of spectral filtering. The third-order dispersion is compensated for by the nonlinear phase shift in the NCPA. With optimization, the system can output 382 fs pulse duration with 20 W average power at 1 MHz repetition rate. The long-term average power fluctuation is measured to be 0.5% in 24 h, and the beam quality factor (
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 091401 (2021)
Stable noise-like pulse generation in all-PM mode-locked Tm-doped fiber laser based on NOLM
Meng Wang, Minqiu Liu, Yewang Chen, Deqin Ouyang, Junqing Zhao, Jihong Pei, and Shuangchen Ruan
A stable noise-like (NL) mode-locked Tm-doped fiber laser (TDFL) relying on a nonlinear optical loop mirror (NOLM) was experimentally presented. Different from the previous NL mode-locked TDFL with NOLM, the entire polarization-maintaining (PM) fiber construction was utilized in our laser cavity, which makes the oscillator have a better resistance to environmental perturbations. The robust TDFL can deliver stable bound-state NL pulses with a pulse envelope tunable from ～14.1 ns to ～23.6 ns and maximum pulse energy of ～40.3 nJ at a repetition rate of ～980.6 kHz. Meanwhile, the all-PM fiber laser shows good power stability (less than ～0.7%) and repeatability.A stable noise-like (NL) mode-locked Tm-doped fiber laser (TDFL) relying on a nonlinear optical loop mirror (NOLM) was experimentally presented. Different from the previous NL mode-locked TDFL with NOLM, the entire polarization-maintaining (PM) fiber construction was utilized in our laser cavity, which makes the oscillator have a better resistance to environmental perturbations. The robust TDFL can deliver stable bound-state NL pulses with a pulse envelope tunable from ～14.1 ns to ～23.6 ns and maximum pulse energy of ～40.3 nJ at a repetition rate of ～980.6 kHz. Meanwhile, the all-PM fiber laser shows good power stability (less than ～0.7%) and repeatability..
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 091402 (2021)
Theoretical analysis of periodically poled LiNbO3 nonlinear mirror and its application in a passively mode-locked Nd:YSAG laser
Lina Zhao, Fangxin Cai, Luyang Tong, Ye Yuan, Wenyu Zhang, and Yangjian Cai
In this paper, we report a passively mode-locked Nd:Y3Sc2Al3O12 (Nd:YSAG) laser using a periodically poled LiNbO3 (PPLN) superlattice. Nonlinear mirror mode locking based on PPLN intracavity frequency doubling was theoretically analyzed. The modulation depth of nonlinear reflectivity of the nonlinear mirror is approximately 8.8%. Optical performances of the mode-locked laser including output power, radio frequency spectrum, and optical spectrum were experimentally investigated. An average output power of 710 mW with a slope efficiency of 14.6% was obtained at the pump power of 6.5 W. The repetition rate is 101.7 MHz, and the signal-to-noise ratio of the mode-locked pulse is 45 dB. The mode-locked pulse width was approximately 9 ps.In this paper, we report a passively mode-locked
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 091403 (2021)
Enhanced optical absorption surface of titanium fabricated by a femtosecond laser assisted with airflow pressure
Xun Li, Ming Li, and Hongjun Liu
We propose an effective way to achieve an enhanced optical absorption surface of titanium alloy 7 (Ti7) fabricated by a femtosecond (fs) laser assisted with airflow pressure. The effect of laser scanning speed and laser power on the surfaces’ morphology and average reflectivity was studied. In order to further reduce the surface’s reflectivity, different airflow pressure was introduced during the fabrication of Ti7 by a fs laser. Furthermore, the average reflectivity of samples fabricated under different laser parameters assisted with airflow was presented. In addition, the high and low temperature tests of all samples were performed to test the stability performance of the hybrid micro/nanostructures in extreme environments. It is demonstrated that the airflow pressure has an important influence on the micro/nanostructures for light trapping, the average reflectivity of which could be as low as 2.31% over a broad band of 250–2300 nm before high and low temperature tests, and the reflection for specific wavelengths can go below 1.5%.We propose an effective way to achieve an enhanced optical absorption surface of titanium alloy 7 (Ti7) fabricated by a femtosecond (fs) laser assisted with airflow pressure. The effect of laser scanning speed and laser power on the surfaces’ morphology and average reflectivity was studied. In order to further reduce the surface’s reflectivity, different airflow pressure was introduced during the fabrication of Ti7 by a fs laser. Furthermore, the average reflectivity of samples fabricated under different laser parameters assisted with airflow was presented. In addition, the high and low temperature tests of all samples were performed to test the stability performance of the hybrid micro/nanostructures in extreme environments. It is demonstrated that the airflow pressure has an important influence on the micro/nanostructures for light trapping, the average reflectivity of which could be as low as 2.31% over a broad band of 250–2300 nm before high and low temperature tests, and the reflection for specific wavelengths can go below 1.5%..
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 091404 (2021)
GSA and ESA dual-wavelength pumped 2.3 μm Tm:YLF laser on the 3H4→3H5 transition
Fei Wang, Haitao Huang, Haiwei Chen, Yushuo Bao, Zihan Li, and Deyuan Shen
The population trapping effect of the F34 level is an important factor limiting the power scaling of the 2.3 μm thulium (Tm) laser on the H34→H35 transition. In this Letter, we demonstrate a novel scheme of ground state absorption (GSA) (H36→H34) and excited state absorption (ESA) (F34→H34) dual-wavelength pumped 2.3 μm Tm lasers. Introducing an ESA pumping process can accurately excite the Tm3+ ions accumulated in the F34 level to the H34 level, constructing a double populating mechanism for the upper laser level H34. A proof-of-principle experimental demonstration of the GSA (785 nm) and ESA (1470 nm) dual-wavelength pumped 2.3 μm Tm:LiYF4 (Tm:YLF) laser was realized. A maximum continuous-wave output power of 1.84 W at 2308 nm was achieved under 785 and 1470 nm dual-wavelength pumping, increased by 60% compared with the case of 785 nm single-wavelength pumping under the same resonator condition. Our work provides an efficient way to achieve higher output power from 2.3 μm Tm-doped lasers on the H34→H35 transition.The population trapping effect of the
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 091405 (2021)
Watt-level continuous-wave intracavity frequency-doubled Pr:YLF-LBO laser at 320 nm
Yunshan Zhang, Jingyu Zou, Wanxin Zheng, Kai Feng, Bin Xu, and Zhenfang Yu
We report on diode-pumped continuous-wave Pr-doped yttrium lithium fluoride (Pr:YLF) laser and its frequency doubling to 320 nm. The maximum output power of the 640 nm fundamental wave reached 3.44 W with a slope efficiency of about 48.3%. Using a type-I phase-matched lithium triborate (LBO) crystal as a frequency doubler, we have achieved 320 nm ultraviolet radiation with a maximum output power of 1.01 W, which is the highest power ever reported under diode pumping, to the best of our knowledge.We report on diode-pumped continuous-wave Pr-doped yttrium lithium fluoride (Pr:YLF) laser and its frequency doubling to 320 nm. The maximum output power of the 640 nm fundamental wave reached 3.44 W with a slope efficiency of about 48.3%. Using a type-I phase-matched lithium triborate (LBO) crystal as a frequency doubler, we have achieved 320 nm ultraviolet radiation with a maximum output power of 1.01 W, which is the highest power ever reported under diode pumping, to the best of our knowledge..
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 091406 (2021)
Optical Design and Fabrication
Micro-projection dynamic backlight for multi-view 3D display
Baichuan Zhao, Ruiying Huang, and Guojiao Lü
A micro-projection dynamic backlight for multi-view three-dimensional (3D) display is proposed. The proposed backlight includes a light emitting diodes (LEDs) array, a lenticular lens array, and a scattering film. The LED array, the lenticular lens, and the scattering film construct a micro-projection structure. In this structure, the LEDs in the array are divided into several groups. The light from each LED group can be projected to the scattering film by the lenticular lens and forms a series of bright stripes. The different LED groups have different horizontal positions, so these bright stripes corresponding to different LED groups also have different horizontal positions. Therefore, they can be used as a dynamic backlight. Because the distance between the LEDs array and the lenticular lens is much larger than the distance between the lenticular lens and the scattering films, the imaging progress will make the width of the bright stripes much smaller than that of the LEDs, and the pitch of the stripes is also decreased. According to the 3D display theory, the bright stripes with small width and pitch help to increase the number of views. Therefore, the proposed micro-projection dynamic backlight is very suitable for multi-view 3D display. An experimental prototype was developed, and the experimental results show that the micro-projection dynamic backlight can correctly complete the directional projection of the parallax images to form a 3D display.A micro-projection dynamic backlight for multi-view three-dimensional (3D) display is proposed. The proposed backlight includes a light emitting diodes (LEDs) array, a lenticular lens array, and a scattering film. The LED array, the lenticular lens, and the scattering film construct a micro-projection structure. In this structure, the LEDs in the array are divided into several groups. The light from each LED group can be projected to the scattering film by the lenticular lens and forms a series of bright stripes. The different LED groups have different horizontal positions, so these bright stripes corresponding to different LED groups also have different horizontal positions. Therefore, they can be used as a dynamic backlight. Because the distance between the LEDs array and the lenticular lens is much larger than the distance between the lenticular lens and the scattering films, the imaging progress will make the width of the bright stripes much smaller than that of the LEDs, and the pitch of the stripes is also decreased. According to the 3D display theory, the bright stripes with small width and pitch help to increase the number of views. Therefore, the proposed micro-projection dynamic backlight is very suitable for multi-view 3D display. An experimental prototype was developed, and the experimental results show that the micro-projection dynamic backlight can correctly complete the directional projection of the parallax images to form a 3D display..
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 092201 (2021)
Optoelectronics
Avalanche mechanism analysis of 4H-SiC n-i-p and p-i-n avalanche photodiodes working in Geiger mode
Linlin Su, Weizong Xu, Dong Zhou, Fangfang Ren, Dunjun Chen, Rong Zhang, Youdou Zheng, and Hai Lu
Understanding detailed avalanche mechanisms is critical for design optimization of avalanche photodiodes (APDs). In this work, avalanche characteristics and single photon counting performance of 4H-SiC n-i-p and p-i-n APDs are compared. By studying the evolution of breakdown voltage as a function of incident light wavelength, it is confirmed that at the deep ultraviolet (UV) wavelength region the avalanche events in 4H-SiC n-i-p APDs are mainly induced by hole-initiated ionization, while electron-initiated ionization is the main cause of avalanche breakdown in 4H-SiC p-i-n APDs. Meanwhile, at the same dark count rate, the single photon counting efficiency of n-i-p APDs is considerably higher than that of p-i-n APDs. The higher performance of n-i-p APDs can be explained by the larger impact ionization coefficient of holes in 4H-SiC. In addition, this is the first time, to the best of our knowledge, to report single photon detection performance of vertical 4H-SiC n-i-p-n APDs.Understanding detailed avalanche mechanisms is critical for design optimization of avalanche photodiodes (APDs). In this work, avalanche characteristics and single photon counting performance of 4H-SiC n-i-p and p-i-n APDs are compared. By studying the evolution of breakdown voltage as a function of incident light wavelength, it is confirmed that at the deep ultraviolet (UV) wavelength region the avalanche events in 4H-SiC n-i-p APDs are mainly induced by hole-initiated ionization, while electron-initiated ionization is the main cause of avalanche breakdown in 4H-SiC p-i-n APDs. Meanwhile, at the same dark count rate, the single photon counting efficiency of n-i-p APDs is considerably higher than that of p-i-n APDs. The higher performance of n-i-p APDs can be explained by the larger impact ionization coefficient of holes in 4H-SiC. In addition, this is the first time, to the best of our knowledge, to report single photon detection performance of vertical 4H-SiC n-i-p-n APDs..
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 092501 (2021)
SNR improvement of 8.2 dB in a self-mixing laser diode interferometer by using the difference signal at the output mirrors [Invited] | Editors' Pick
Silvano Donati, and Michele Norgia
At the mirrors of a laser diode self-mixing interferometer, the output beams carry anti-correlated (i.e., in phase opposition) interferometric signals, whereas the superposed noise fluctuations are (partially) correlated. Therefore, by using an instrumental output of the interferometer as the difference of the two, we double the amplitude of the self-mixing useful signal, while the superposed noise is reduced. To validate the idea, we first calculate the noise reduction by means of a second-quantization model, finding that in a laser diode the signal-to-noise ratio (SNR) can be improved by 8.2 dB, typically. Then, we also carry out an experimental measurement of SNR and find very good agreement with the theoretical result.At the mirrors of a laser diode self-mixing interferometer, the output beams carry anti-correlated (i.e., in phase opposition) interferometric signals, whereas the superposed noise fluctuations are (partially) correlated. Therefore, by using an instrumental output of the interferometer as the difference of the two, we double the amplitude of the self-mixing useful signal, while the superposed noise is reduced. To validate the idea, we first calculate the noise reduction by means of a second-quantization model, finding that in a laser diode the signal-to-noise ratio (SNR) can be improved by 8.2 dB, typically. Then, we also carry out an experimental measurement of SNR and find very good agreement with the theoretical result..
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 092502 (2021)
Ultrafast Optics and Attosecond/High-field Physics
Generation of 601 fs pulse from an 8 kHz Nd:YVO4 picosecond laser by multi-pass-cell spectral broadening
Jiajun Song, Zhaohua Wang, Xianzhi Wang, Renchong Lü, Hao Teng, Jiangfeng Zhu, and Zhiyi Wei
We demonstrate nonlinear pulse compression of an 8 kHz Nd:YVO4 picosecond laser using the multi-pass-cell (MPC) technique with fused silica as the nonlinear medium. The pulse duration is compressed from 12.5 ps to 601 fs, corresponding to a pulse shortening factor of 20.8. The output pulse energy is 154 μJ with an efficiency of 74.5%. To the best of our knowledge, this is the highest pulse compression ratio achieved in a single-stage MPC with bulk material as the nonlinear medium. The laser power stability and the beam quality (M2) before and after the MPC are also experimentally studied. Both the laser power stability and the beam quality are barely deteriorated by the MPC device.We demonstrate nonlinear pulse compression of an 8 kHz Nd:
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 093201 (2021)
Visual Optics and Displays
High-speed playback of spatiotemporal division multiplexing holographic 3D video stored in a solid-state drive using a digital micromirror device
Kohei Suzuki, Minori Tao, Yuki Maeda, Hirotaka Nakayama, Ren Noguchi, Minoru Oikawa, Yuichiro Mori, Takashi Kakue, Tomoyoshi Shimobaba, Tomoyoshi Ito, and Naoki Takada
We propose a high-speed playback method for the spatiotemporal division multiplexing electroholographic three-dimensional (3D) video stored in a solid-state drive (SSD) using a digital micromirror device. The spatiotemporal division multiplexing electroholography prevents deterioration in the reconstructed 3D video from a 3D object comprising many object points. In the proposed method, the stored data is remarkably reduced using the packing technique, and the computer-generated holograms are played back at high speed. Consequently, we successfully reconstructed a clear 3D video of a 3D object comprising approximately 1,100,000 points at 60 frames per second by reducing the reading time of the stored data from an SSD.We propose a high-speed playback method for the spatiotemporal division multiplexing electroholographic three-dimensional (3D) video stored in a solid-state drive (SSD) using a digital micromirror device. The spatiotemporal division multiplexing electroholography prevents deterioration in the reconstructed 3D video from a 3D object comprising many object points. In the proposed method, the stored data is remarkably reduced using the packing technique, and the computer-generated holograms are played back at high speed. Consequently, we successfully reconstructed a clear 3D video of a 3D object comprising approximately 1,100,000 points at 60 frames per second by reducing the reading time of the stored data from an SSD..
Chinese Optics Letters
- Publication Date: Sep. 10, 2021
- Vol. 19, Issue 9, 093301 (2021)
About the Cover
Mode division multiplexing (MDM) technology connecting photonic integrated circuits and fiber optic transmission, brings great improvements on the density, efficiency and capacity of optical interconnection, and promotes it keep going towards the “Moore’s law” trend of optical communication.
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