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Lasers, Optical Amplifiers, and Laser Optics|153 Article(s)
Design of a high frequency accuracy heterodyne laser source working in a wide temperature range
Hongxing Yang, Yan Wang, Ziqi Yin, Pengcheng Hu, Ruitao Yang, and Jing Li
To ensure the frequency accuracy of a heterodyne laser source in the ambient temperature range of -20°C to 40°C, a dual-longitudinal-mode thermally stabilized He–Ne laser based on non-equilibrium power locking was designed. The ambient adaptive preheating temperature setting scheme ensured the laser could operate normally in the range of -20°C to 40°C. The non-equilibrium power-locked frequency stabilization scheme compensated for the frequency drift caused by different stabilization temperatures. The experimental results indicated that the frequency accuracy of the laser designed in this study could reach 5.2 × 10-9 in the range of -20°C to 40°C. To ensure the frequency accuracy of a heterodyne laser source in the ambient temperature range of -20°C to 40°C, a dual-longitudinal-mode thermally stabilized He–Ne laser based on non-equilibrium power locking was designed. The ambient adaptive preheating temperature setting scheme ensured the laser could operate normally in the range of -20°C to 40°C. The non-equilibrium power-locked frequency stabilization scheme compensated for the frequency drift caused by different stabilization temperatures. The experimental results indicated that the frequency accuracy of the laser designed in this study could reach 5.2 × 10-9 in the range of -20°C to 40°C.
Chinese Optics Letters
- Publication Date: Apr. 25, 2024
- Vol. 22, Issue 4, 041407 (2024)
5 kW-level single-mode fiber amplifier based on low-numerical-aperture fiber
Yisha Chen, Yun Ye, Liangjin Huang, Huan Yang, Hanshuo Wu, Zhiping Yan, Zhiyong Pan, Xiaolin Wang, Zefeng Wang, and Pu Zhou
A low-numerical-aperture (NA) concept enables large-mode-area fiber with better single-mode operation ability, which is beneficial for transverse mode instability and nonlinear effects suppression. In this contribution, we reported a high-power fiber amplifier based on a piece of self-developed large-mode-area low-NA fiber with a core NA of 0.049 and a core/inner cladding diameter of 25/400 µm. The influence of the pump wavelength and fiber length on the power scaling potential of the fiber amplifier is systematically investigated. As a result, an output of 4.80 kW and a beam quality factor of ∼1.33 were finally obtained, which is the highest output power ever reported in a fiber amplifier exploiting the low-NA fiber. The results reveal that low-NA fibers have superiority in power scaling and beam quality maintenance at high power levels. A low-numerical-aperture (NA) concept enables large-mode-area fiber with better single-mode operation ability, which is beneficial for transverse mode instability and nonlinear effects suppression. In this contribution, we reported a high-power fiber amplifier based on a piece of self-developed large-mode-area low-NA fiber with a core NA of 0.049 and a core/inner cladding diameter of 25/400 µm. The influence of the pump wavelength and fiber length on the power scaling potential of the fiber amplifier is systematically investigated. As a result, an output of 4.80 kW and a beam quality factor of ∼1.33 were finally obtained, which is the highest output power ever reported in a fiber amplifier exploiting the low-NA fiber. The results reveal that low-NA fibers have superiority in power scaling and beam quality maintenance at high power levels.
Chinese Optics Letters
- Publication Date: Apr. 18, 2024
- Vol. 22, Issue 4, 041404 (2024)
High-power all-fiber linearly polarized Yb-doped chirped pulse amplifier based on active polarization control
Tao Wang, Shuai Ren, Hongxiang Chang, Bo Ren, Kun Guo, Can Li, Pengfei Ma, Jinyong Leng, and Pu Zhou
High-power ultrafast laser amplification based on a non-polarization maintaining fiber chirped pulse amplifier is demonstrated. The active polarization control technology based on the root-mean-square propagation (RMS-prop) algorithm is employed to guarantee a linearly polarized output from the system. A maximum output power of 402.3 W at a repetition rate of 80 MHz is realized with a polarization extinction ratio (PER) of > 11.4 dB. In addition, the reliable operation of the system is verified by examining the stability and noise properties of the amplified laser. The M2 factor of the laser beam at the highest output power is measured to be less than 1.15, indicating a diffraction-limited beam quality. Finally, the amplified laser pulse is temporally compressed to 755 fs with a highest average power of 273.8 W. This is the first time, to the best of our knowledge, that the active polarization control technology was introduced into the high-power ultrafast fiber amplifier. High-power ultrafast laser amplification based on a non-polarization maintaining fiber chirped pulse amplifier is demonstrated. The active polarization control technology based on the root-mean-square propagation (RMS-prop) algorithm is employed to guarantee a linearly polarized output from the system. A maximum output power of 402.3 W at a repetition rate of 80 MHz is realized with a polarization extinction ratio (PER) of > 11.4 dB. In addition, the reliable operation of the system is verified by examining the stability and noise properties of the amplified laser. The M2 factor of the laser beam at the highest output power is measured to be less than 1.15, indicating a diffraction-limited beam quality. Finally, the amplified laser pulse is temporally compressed to 755 fs with a highest average power of 273.8 W. This is the first time, to the best of our knowledge, that the active polarization control technology was introduced into the high-power ultrafast fiber amplifier.
Chinese Optics Letters
- Publication Date: Apr. 17, 2024
- Vol. 22, Issue 4, 041403 (2024)
Eye-safe intra-cavity diamond cascaded Raman laser with high peak-power and narrow linewidth
Xiaobo Mi, Chaonan Lin, Yongsheng Hu, Houjie Ma, Jiuru He, Fengying Ma, Li Fan, and Chongxin Shan
The 1.4–1.8 µm eye-safe lasers have been widely used in the fields of laser medicine and laser detection and ranging. The diamond Raman lasers are capable of delivering excellent characteristics, such as good beam quality concomitantly with high output power. The intra-cavity diamond Raman lasers have the advantages of compactness and low Raman thresholds compared to the external-cavity Raman lasers. However, to date, the intra-cavity diamond cascaded Raman lasers in the spectral region of the eye-safe laser have an output power of only a few hundred milliwatts. A 1485 nm Nd:YVO4/diamond intra-cavity cascaded Raman laser is reported in this paper. The mode matching and stability of the cavity were optimally designed by a V-shaped folded cavity, which yielded an average output power of up to 2.2 W at a pulse repetition frequency of 50 kHz with a diode to second-Stokes conversion efficiency of 8.1%. Meanwhile, the pulse width of the second-Stokes laser was drastically reduced from 60 ns of the fundamental laser to 1.1 ns, which resulted in a high peak power of 40 kW. The device also exhibited single longitudinal mode with a narrow spectral width of < 0.02 nm. The 1.4–1.8 µm eye-safe lasers have been widely used in the fields of laser medicine and laser detection and ranging. The diamond Raman lasers are capable of delivering excellent characteristics, such as good beam quality concomitantly with high output power. The intra-cavity diamond Raman lasers have the advantages of compactness and low Raman thresholds compared to the external-cavity Raman lasers. However, to date, the intra-cavity diamond cascaded Raman lasers in the spectral region of the eye-safe laser have an output power of only a few hundred milliwatts. A 1485 nm Nd:YVO4/diamond intra-cavity cascaded Raman laser is reported in this paper. The mode matching and stability of the cavity were optimally designed by a V-shaped folded cavity, which yielded an average output power of up to 2.2 W at a pulse repetition frequency of 50 kHz with a diode to second-Stokes conversion efficiency of 8.1%. Meanwhile, the pulse width of the second-Stokes laser was drastically reduced from 60 ns of the fundamental laser to 1.1 ns, which resulted in a high peak power of 40 kW. The device also exhibited single longitudinal mode with a narrow spectral width of < 0.02 nm.
Chinese Optics Letters
- Publication Date: Apr. 18, 2024
- Vol. 22, Issue 4, 041402 (2024)
Experiments and simulation on the overall DMG of long-haul cascade FM-EDFA systems
Xinrui Jiang, Baojian Wu, Wei Yan, Feng Wen, and Kun Qiu
All-fiber few-mode erbium-doped fiber amplifiers (FM-EDFAs) with isolation and wavelength division multiplexers (IWDMs) have been developed to enable flexible pumping in different directions. The FM-EDFA can achieve >30 dB modal gain with <0.3 dB differential modal gain (DMG). We experimentally simulate the DMG performance of a cascade FM-EDFA system using the equivalent spectrum method. The overall DMG reaches 1.84 dB after 10-stage amplification. We also build a recirculating loop to simulate the system, and the developed FM-EDFA can support transmission up to 3270 km within a 2 dB overall DMG by optimizing the few-mode fiber length in the loop. All-fiber few-mode erbium-doped fiber amplifiers (FM-EDFAs) with isolation and wavelength division multiplexers (IWDMs) have been developed to enable flexible pumping in different directions. The FM-EDFA can achieve >30 dB modal gain with <0.3 dB differential modal gain (DMG). We experimentally simulate the DMG performance of a cascade FM-EDFA system using the equivalent spectrum method. The overall DMG reaches 1.84 dB after 10-stage amplification. We also build a recirculating loop to simulate the system, and the developed FM-EDFA can support transmission up to 3270 km within a 2 dB overall DMG by optimizing the few-mode fiber length in the loop.
Chinese Optics Letters
- Publication Date: Apr. 17, 2024
- Vol. 22, Issue 4, 041401 (2024)
Dynamic range expansion for optical frequency shift detection based on multiple harmonics
Yanru Zhou, Lifan Fan, Kai Xu, Wenyao Liu, Enbo Xing, Jun Tang, and Jun Liu
Sensors based on optical resonators often have their measurement range limited by their cavity linewidth, particularly in the measurement of time-varying signals. This paper introduces a method for optical frequency shift detection using multiple harmonics to expand the dynamic range of sensors based on optical resonators. The proposed method expands the measurement range of optical frequency shift beyond the cavity linewidth while maintaining measurement accuracy. The theoretical derivation of this method is carried out based on the equation of motion for an optical resonator and the recursive relationship of the Bessel function. Experimental results show that the dynamic range is expanded to 4 times greater than the conventional first harmonic method while still maintaining accuracy. Furthermore, we present an objective analysis of the correlation between the expansion factor of the method and the linewidth and free spectrum of the optical resonator. Sensors based on optical resonators often have their measurement range limited by their cavity linewidth, particularly in the measurement of time-varying signals. This paper introduces a method for optical frequency shift detection using multiple harmonics to expand the dynamic range of sensors based on optical resonators. The proposed method expands the measurement range of optical frequency shift beyond the cavity linewidth while maintaining measurement accuracy. The theoretical derivation of this method is carried out based on the equation of motion for an optical resonator and the recursive relationship of the Bessel function. Experimental results show that the dynamic range is expanded to 4 times greater than the conventional first harmonic method while still maintaining accuracy. Furthermore, we present an objective analysis of the correlation between the expansion factor of the method and the linewidth and free spectrum of the optical resonator.
Chinese Optics Letters
- Publication Date: Apr. 25, 2024
- Vol. 22, Issue 4, 041201 (2024)
Generation and observation of multiple solitons from a mid-infrared ultrafast fiber laser
Mengyuan Li, Yufeng Song, Chunxiang Zhang, Zhenhong Wang, and Jun Liu
We demonstrate the generation of a unique regime of multiple solitons in a Tm-doped ultrafast fiber laser at ∼1938.72 nm. The temporal pulse-to-pulse separation among the multiple solitons, 10 in a single-pulse bunch, increases from 0.89 ns to 1.85 ns per round trip. In addition, with the increasing pump power, the number of bunched solitons increases from 3 up to 24 linearly, while the average time separation in the soliton bunch varies irregularly between ∼0.80 and ∼1.52 ns. These results contribute to a more profound comprehension of nonlinear pulse dynamics in ultrafast fiber lasers. We demonstrate the generation of a unique regime of multiple solitons in a Tm-doped ultrafast fiber laser at ∼1938.72 nm. The temporal pulse-to-pulse separation among the multiple solitons, 10 in a single-pulse bunch, increases from 0.89 ns to 1.85 ns per round trip. In addition, with the increasing pump power, the number of bunched solitons increases from 3 up to 24 linearly, while the average time separation in the soliton bunch varies irregularly between ∼0.80 and ∼1.52 ns. These results contribute to a more profound comprehension of nonlinear pulse dynamics in ultrafast fiber lasers.
Chinese Optics Letters
- Publication Date: Mar. 04, 2024
- Vol. 22, Issue 3, 031405 (2024)
Stable ultraviolet ultrafast laser based on all-polarization-maintaining fiber femtosecond laser
Hao Tian, Zhe Zhu, Wei Lin, Zihao Li, Junpeng Wen, Hao Xiu, Yiheng Fan, Chiyi Wei, Xiaoming Wei, and Zhongmin Yang
We report a high-stability ultrafast ultraviolet (UV) laser source at 352 nm by exploring an all-fiber, all-polarization-maintaining (all-PM), Yb-doped femtosecond fiber laser at 1060 nm. The output power, pulse width, and optical spectrum width of the fiber laser are 6 W, 244 fs, and 17.5 nm, respectively. The UV ultrashort pulses at a repetition rate of 28.9 MHz are generated by leveraging single-pass second-harmonic generation in a 1.3-mm-long BiB3O6 (BIBO) and sum frequency generation in a 5.1-mm-long BIBO. The maximum UV output power is 596 mW. The root mean square error of the output power of UV pulses is 0.54%. This laser, with promising stability, is expected to be a nice source for frontier applications in the UV wavelength window. We report a high-stability ultrafast ultraviolet (UV) laser source at 352 nm by exploring an all-fiber, all-polarization-maintaining (all-PM), Yb-doped femtosecond fiber laser at 1060 nm. The output power, pulse width, and optical spectrum width of the fiber laser are 6 W, 244 fs, and 17.5 nm, respectively. The UV ultrashort pulses at a repetition rate of 28.9 MHz are generated by leveraging single-pass second-harmonic generation in a 1.3-mm-long BiB3O6 (BIBO) and sum frequency generation in a 5.1-mm-long BIBO. The maximum UV output power is 596 mW. The root mean square error of the output power of UV pulses is 0.54%. This laser, with promising stability, is expected to be a nice source for frontier applications in the UV wavelength window.
Chinese Optics Letters
- Publication Date: Mar. 22, 2024
- Vol. 22, Issue 3, 031404 (2024)
Bright/dark switchable mode-locked fiber laser based on alcohol
Wenyan Zhang, Huijie Jiang, Kun Yang, Nannan Liu, Lijie Geng, Yunqi Hao, Tianhao Xian, and Li Zhan
A passively switchable erbium-doped fiber laser based on alcohol as the saturable absorber (SA) has been demonstrated. The SA is prepared by filling the gap between two optical patch cords with alcohol to form a sandwich structure. The modulation depth of the alcohol–SA is measured to be 6.4%. By appropriately adjusting the pump power and the polarization state in the cavity, three kinds of mode-locked pulse patterns can be achieved and switched, including bright pulse, bright/dark soliton pair, and dark pulse. These different soliton emissions all operate at the fundamental frequency state, with a repetition rate of 20.05 MHz and a central wavelength of ∼1563 nm. To the best of our knowledge, this is the first demonstration of a switchable soliton fiber laser using alcohol as the SA. The experimental results further indicate that organic liquid-like alcohol has great potential for constructing ultrafast lasers. A passively switchable erbium-doped fiber laser based on alcohol as the saturable absorber (SA) has been demonstrated. The SA is prepared by filling the gap between two optical patch cords with alcohol to form a sandwich structure. The modulation depth of the alcohol–SA is measured to be 6.4%. By appropriately adjusting the pump power and the polarization state in the cavity, three kinds of mode-locked pulse patterns can be achieved and switched, including bright pulse, bright/dark soliton pair, and dark pulse. These different soliton emissions all operate at the fundamental frequency state, with a repetition rate of 20.05 MHz and a central wavelength of ∼1563 nm. To the best of our knowledge, this is the first demonstration of a switchable soliton fiber laser using alcohol as the SA. The experimental results further indicate that organic liquid-like alcohol has great potential for constructing ultrafast lasers.
Chinese Optics Letters
- Publication Date: Mar. 07, 2024
- Vol. 22, Issue 3, 031403 (2024)
22 kW near-diffraction-limited Yb:YAG slab laser amplifier without adaptive optics correction
Dan Wang, Ping He, Tangjian Zhou, Mi Li, Yingchen Wu, Yanan Wang, Jianli Shang, Qingsong Gao, Kai Zhang, Chun Tang, and Rihong Zhu
A high-power CW Yb:YAG slab laser amplifier with no adaptive optics correction has been experimentally established. At room temperature, the amplifier emits a power of 22 kW with an average beam quality (β) of less than 3 in 0.5 min. To our knowledge, this is the brightest slab laser without closed-loop adaptive optics demonstrated to date. In addition, an extracted power of 17 kW with an optical extraction efficiency of 33%, corresponding to a residual optical path difference of less than 0.5 µm, is achieved with the single Yb:YAG slab gain module. The slab gain module has the potential to be scalable to higher powers while maintaining good beam quality. This makes a high-power solid-state laser system simpler and more robust. A high-power CW Yb:YAG slab laser amplifier with no adaptive optics correction has been experimentally established. At room temperature, the amplifier emits a power of 22 kW with an average beam quality (β) of less than 3 in 0.5 min. To our knowledge, this is the brightest slab laser without closed-loop adaptive optics demonstrated to date. In addition, an extracted power of 17 kW with an optical extraction efficiency of 33%, corresponding to a residual optical path difference of less than 0.5 µm, is achieved with the single Yb:YAG slab gain module. The slab gain module has the potential to be scalable to higher powers while maintaining good beam quality. This makes a high-power solid-state laser system simpler and more robust.
Chinese Optics Letters
- Publication Date: Mar. 21, 2024
- Vol. 22, Issue 3, 031402 (2024)
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