Identifying self-trapped excitons in 2D perovskites by Raman spectroscopy [Invited]
Junze Li, Junchao Hu, Jiaqi Ma, Xinglin Wen, and Dehui Li
Two-dimensional (2D) perovskites exhibit broadband emission due to strong exciton–phonon coupling-induced self-trapped excitons and thus would find important applications in the field of white-light emitting devices. However, the available identifying methods for self-trapped excitons are currently rather limited and complex. Here, we identify the existence of self-trapped excitons by Raman spectroscopy in both excited and non-excited states. Under excited states, the shifting of the Raman peak indicates the presence of the lattice distortion, which together with the extra Raman scattering peak reveals the presence of self-trapped excitons. Our work provides an alternative simple method to study self-trapped excitons in 2D perovskites.Two-dimensional (2D) perovskites exhibit broadband emission due to strong exciton–phonon coupling-induced self-trapped excitons and thus would find important applications in the field of white-light emitting devices. However, the available identifying methods for self-trapped excitons are currently rather limited and complex. Here, we identify the existence of self-trapped excitons by Raman spectroscopy in both excited and non-excited states. Under excited states, the shifting of the Raman peak indicates the presence of the lattice distortion, which together with the extra Raman scattering peak reveals the presence of self-trapped excitons. Our work provides an alternative simple method to study self-trapped excitons in 2D perovskites.
- Jul. 23, 2021
- Chinese Optics Letters
- Vol.19 Issue, 10 103001 (2021)
- DOI：10.3788/COL202119.103001
Multi-focused droplet lens array inspired by movable-type printing technology
Bo Dai, Zhengmeng Zhou, Yan Long, Mingliang Pan, Zeyuan Song, and Dawei Zhang
A straightforward, cost-effective scheme for fabricating multi-focus droplet lens arrays is proposed. Mini lenses can be rapidly produced by dripping liquid-state polydimethylsiloxane droplets on the square glass substrate. The focal length of the lenses can be precisely controlled by adjusting the mass of the droplet. A group of prepared mini lenses can be flexibly assembled in a three-dimensional printed mount. The lenses are tightly packed together, ensuring a high filling factor of the lens array. The lens array consisting of the mini lenses with a proper combination of focal length can capture images of interests at different depth.A straightforward, cost-effective scheme for fabricating multi-focus droplet lens arrays is proposed. Mini lenses can be rapidly produced by dripping liquid-state polydimethylsiloxane droplets on the square glass substrate. The focal length of the lenses can be precisely controlled by adjusting the mass of the droplet. A group of prepared mini lenses can be flexibly assembled in a three-dimensional printed mount. The lenses are tightly packed together, ensuring a high filling factor of the lens array. The lens array consisting of the mini lenses with a proper combination of focal length can capture images of interests at different depth.
- Jul. 23, 2021
- Chinese Optics Letters
- Vol.19 Issue, 10 102201 (2021)
- DOI：10.3788/COL202119.102201
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.
- Jul. 08, 2021
- Chinese Optics Letters
- Vol.19 Issue, 9 091201 (2021)
- DOI：10.3788/COL202119.091201
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 (
- Jun. 02, 2021
- Chinese Optics Letters
- Vol.19 Issue, 9 091401 (2021)
- DOI：10.3788/COL202119.091401
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.
- Jun. 15, 2021
- Chinese Optics Letters
- Vol.19 Issue, 9 093701 (2021)
- DOI：10.3788/COL202119.093701
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.
- Jun. 15, 2021
- Chinese Optics Letters
- Vol.19 Issue, 9 091406 (2021)
- DOI：10.3788/COL202119.091406
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.
- Jul. 08, 2021
- Chinese Optics Letters
- Vol.19 Issue, 9 091204 (2021)
- DOI：10.3788/COL202119.091204
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Special Issue on High Power Laser Science and Engineering 2021 (2021)
Submission Open:25 February 2021; Submission Deadline: 31 July 2021
Editor (s): Colin Danson, Jianqiang Zhu
Submission Open:1 January 2021; Submission Deadline: 1 July 2021
Editor (s): Max Lederer, Haixiao Deng, Sergio Carbajo
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