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Nonlinear Optics|134 Article(s)
Cascaded optical parameter oscillator within lithium tantalate microdisk based on two periodically poled structures
Kun Zhang, Yifan Chen, Chongyang Xu, Hongquan Yao, Jian Ning, Xinjie Lü, Gang Zhao, Peng Zhan, Zhenda Xie, and Shining Zhu
The whispering gallery resonator (WGR) represents a promising avenue for the miniaturization of optical devices, while cascaded optical parameter oscillator (OPO) processes have not been realized in the WGR, to the best of our knowledge. We present a microdisk with quality factors up to 3.2 × 107, then embed two quasi-phase-matching structures inside it to demonstrate cascaded OPO. The cascaded OPO exhibits the same idler light output with the threshold of 32.7 mW at 36°C (1063.8 nm → 1566.6 nm + 3314.6 nm/1566.6 nm → 2970.4 nm + 3314.6 nm), while the operating threshold of OPO without cascade process is 4.32 mW. Moreover, diverse cascaded processes are observed, with the longest output wavelength reaching 4802.9 nm. Our results suggest the potential for a low-threshold cascade OPO based on WGR. The whispering gallery resonator (WGR) represents a promising avenue for the miniaturization of optical devices, while cascaded optical parameter oscillator (OPO) processes have not been realized in the WGR, to the best of our knowledge. We present a microdisk with quality factors up to 3.2 × 107, then embed two quasi-phase-matching structures inside it to demonstrate cascaded OPO. The cascaded OPO exhibits the same idler light output with the threshold of 32.7 mW at 36°C (1063.8 nm → 1566.6 nm + 3314.6 nm/1566.6 nm → 2970.4 nm + 3314.6 nm), while the operating threshold of OPO without cascade process is 4.32 mW. Moreover, diverse cascaded processes are observed, with the longest output wavelength reaching 4802.9 nm. Our results suggest the potential for a low-threshold cascade OPO based on WGR.
Chinese Optics Letters
- Publication Date: Apr. 10, 2025
- Vol. 23, Issue 4, 041902 (2025)
Nonlinear Cherenkov radiation in rotatory nonlinear optics
Zhongmian Zhang, Dazhi Lu, Haohai Yu, Huaijin Zhang, and Yicheng Wu
Nonlinear Cherenkov radiation is a phenomenon of light first observed in 1970 that can be manipulated by phase matching conditions. However, under a rotatory symmetry, the nonlinear Cherenkov radiation was still untouched, where the rotation parameters in optics would introduce an additional phase to the beam, change the phase velocity of the electromagnetic wave, and lead to novel optical phenomena. Here, we introduce rotation as a new freedom and study the nonlinear Cherenkov radiation in optically rotatory crystals in theory. With a quartz crystal as the representative, we derive theoretical variations, which show that the phase velocity of the crystal-coupled wave is found to be accelerated or decelerated by the rotational angular velocity, corresponding to the change of the Cherenkov radiation angle. In addition, the variation on the effective nonlinear coefficient of quartz crystals with rotational polarization direction is analyzed theoretically and used to simulate the Cherenkov ring distribution in rotatory nonlinear optics. This work introduces the rotation parameter into the non-collinear phase matching process and may inspire the development of modern photonics and physics in rotatory frames. Nonlinear Cherenkov radiation is a phenomenon of light first observed in 1970 that can be manipulated by phase matching conditions. However, under a rotatory symmetry, the nonlinear Cherenkov radiation was still untouched, where the rotation parameters in optics would introduce an additional phase to the beam, change the phase velocity of the electromagnetic wave, and lead to novel optical phenomena. Here, we introduce rotation as a new freedom and study the nonlinear Cherenkov radiation in optically rotatory crystals in theory. With a quartz crystal as the representative, we derive theoretical variations, which show that the phase velocity of the crystal-coupled wave is found to be accelerated or decelerated by the rotational angular velocity, corresponding to the change of the Cherenkov radiation angle. In addition, the variation on the effective nonlinear coefficient of quartz crystals with rotational polarization direction is analyzed theoretically and used to simulate the Cherenkov ring distribution in rotatory nonlinear optics. This work introduces the rotation parameter into the non-collinear phase matching process and may inspire the development of modern photonics and physics in rotatory frames.
Chinese Optics Letters
- Publication Date: Apr. 16, 2025
- Vol. 23, Issue 4, 041901 (2025)
THz radiation coherent accumulation along a two-color laser filament in air
Zeliang Zhang, Qiang Su, Lu Sun, Pengfei Qi, Zhiqiang Yu, Olga Kosareva, and Weiwei Liu
Terahertz (THz) radiation generation by two-color femtosecond laser filamentation is a promising path for high-intensity THz source development. The intrinsic characteristics of the filament, especially its length, play a crucial role in determining the THz radiation strength. However, a detailed analysis of the underlying physical mechanism and the quantitative correlation between the laser filament length and the THz radiation intensity under a high-peak-power driving laser is still lacking. In this paper, the effect of filament length on the THz radiation is investigated by modulating the basic characteristics of the two-color laser field and changing the focal length. Experimental results show that the long filament length is advantageous for improving THz radiation intensity. The theoretical simulation indicates that enhancement of THz radiation arises from coherent accumulation of THz wave produced at each cross-section along the filament. These insights suggest that extending the filament length is an effective scheme to enhance the intensity of THz radiation generated by the two-color femtosecond laser filament. Terahertz (THz) radiation generation by two-color femtosecond laser filamentation is a promising path for high-intensity THz source development. The intrinsic characteristics of the filament, especially its length, play a crucial role in determining the THz radiation strength. However, a detailed analysis of the underlying physical mechanism and the quantitative correlation between the laser filament length and the THz radiation intensity under a high-peak-power driving laser is still lacking. In this paper, the effect of filament length on the THz radiation is investigated by modulating the basic characteristics of the two-color laser field and changing the focal length. Experimental results show that the long filament length is advantageous for improving THz radiation intensity. The theoretical simulation indicates that enhancement of THz radiation arises from coherent accumulation of THz wave produced at each cross-section along the filament. These insights suggest that extending the filament length is an effective scheme to enhance the intensity of THz radiation generated by the two-color femtosecond laser filament.
Chinese Optics Letters
- Publication Date: Feb. 28, 2025
- Vol. 23, Issue 2, 021902 (2025)
Wave interference under self-phase modulation and triple frequency generation owing to few-cycle terahertz pulses propagating in a cubic nonlinear medium
Ilia Artser, Maksim Melnik, Anton Tcypkin, Igor Gurov, and Sergei Kozlov
Recently, in the field of nonlinear optics of the terahertz frequency range, numerous unique features have been discovered that distinguish it advantageously from nonlinear optics of the optical frequency range. This study demonstrates that the interference of radiations generated at triple frequencies and those due to self-phase modulation in a cubic nonlinear medium can be either constructive or destructive, depending on the parameters of the pulse at the input of the medium. As a result, for a single-cycle pulse, mutual attenuation of these effects is observed by a factor of 20, while for a single and a half-cycle pulse, mutual enhancement occurs by a factor of 1.7. The obtained features are in good agreement with existing experimental data. Thus, by varying the parameters of few-cycle terahertz waves, it is possible to control the nonlinear processes observed in optical media. This will allow for the future development of light-to-light control devices based on these principles. Recently, in the field of nonlinear optics of the terahertz frequency range, numerous unique features have been discovered that distinguish it advantageously from nonlinear optics of the optical frequency range. This study demonstrates that the interference of radiations generated at triple frequencies and those due to self-phase modulation in a cubic nonlinear medium can be either constructive or destructive, depending on the parameters of the pulse at the input of the medium. As a result, for a single-cycle pulse, mutual attenuation of these effects is observed by a factor of 20, while for a single and a half-cycle pulse, mutual enhancement occurs by a factor of 1.7. The obtained features are in good agreement with existing experimental data. Thus, by varying the parameters of few-cycle terahertz waves, it is possible to control the nonlinear processes observed in optical media. This will allow for the future development of light-to-light control devices based on these principles.
Chinese Optics Letters
- Publication Date: Mar. 05, 2025
- Vol. 23, Issue 2, 021901 (2025)
Stable cascaded femtosecond optical parametric amplifiers in the NIR-I region at 50 MHz
Xiaoxuan Zhu, Jue Wang, Xuechen Gao, Jintao Fan, and Minglie Hu
We experimentally demonstrate a continuous-wave (CW) injection-seeded cascaded optical parametric amplifier (OPA) for generating femtosecond pulses in the NIR-I spectral region. Utilizing a cascaded two-stage configuration, our system achieves an output of 347 mW of NIR radiation centered at 792 nm, combined with a pulse duration of 171 fs at a repetition rate of 50 MHz. The CW seeding intrinsically ensures superior pulse-to-pulse and long-term power stability. Our measurements indicate a relative intensity noise (RIN) of 2.2% root mean square (RMS) (integrated from 3.3 Hz to 2.5 MHz) and an RMS power stability as low as 0.63% over a duration of 90 min. Moreover, the beam quality of the output beam is near-diffraction-limited, with M2 factors of MX2 = 1.11 and MY2 = 1.29. We believe that this type of laser source is capable of delivering stable femtosecond pulses within the NIR-I spectral range and can serve as an ideal solution for various applications including biophotonics, microscopy, and laser processing. We experimentally demonstrate a continuous-wave (CW) injection-seeded cascaded optical parametric amplifier (OPA) for generating femtosecond pulses in the NIR-I spectral region. Utilizing a cascaded two-stage configuration, our system achieves an output of 347 mW of NIR radiation centered at 792 nm, combined with a pulse duration of 171 fs at a repetition rate of 50 MHz. The CW seeding intrinsically ensures superior pulse-to-pulse and long-term power stability. Our measurements indicate a relative intensity noise (RIN) of 2.2% root mean square (RMS) (integrated from 3.3 Hz to 2.5 MHz) and an RMS power stability as low as 0.63% over a duration of 90 min. Moreover, the beam quality of the output beam is near-diffraction-limited, with M2 factors of MX2 = 1.11 and MY2 = 1.29. We believe that this type of laser source is capable of delivering stable femtosecond pulses within the NIR-I spectral range and can serve as an ideal solution for various applications including biophotonics, microscopy, and laser processing.
Chinese Optics Letters
- Publication Date: Feb. 05, 2025
- Vol. 23, Issue 1, 011902 (2025)
Dispersions of two-photon and three-photon absorption in GaS films from 540 to 1600 nm
Yijie Wang, Jinhong Liu, Yanqing Ge, Erkang Li, Lili Zhao, Chunhui Lu, Yixuan Zhou, and Xinlong Xu
The development of nonlinear optical materials with strong multiphoton absorption (MPA) is crucial for the design of ultrafast nonlinear optical devices, such as optical limiters and all-optical switchers. In this study, we present the wavelength-dependent coefficients of two-photon absorption (2PA) and three-photon absorption (3PA) in a GaS film across a broad range of wavelengths from 540 to 1600 nm. The observed dispersions in the 2PA and 3PA coefficients align well with the widely used two-band approximation model applied to direct bandgap semiconductors. Notably, the GaS film exhibits exceptional MPA properties with a maximum 2PA coefficient of 19.89 cm/GW at 620 nm and a maximum 3PA coefficient of 4.88 cm3/GW2 at 1500 nm. The GaS film surpasses those found in traditional wide-bandgap semiconductors like β-Ga2O3, GaN, ZnO, and ZnS while remaining comparable to monolayer MoS2, CsPbBr3, and (C4H9NH3)2PbBr4 perovskites. By employing a simplified two-energy-level model analysis, our results indicate that these large MPA coefficients are primarily determined by the remarkable absorption cross sections, which are approximately 4.82 × 10-52·cm4·s·photon-1 at 620 nm for 2PA and 8.17 × 10-80·cm6·s2·photon-2 at 1500 nm for 3PA. Our findings demonstrate significant potential for utilizing GaS films in nonlinear optical applications. The development of nonlinear optical materials with strong multiphoton absorption (MPA) is crucial for the design of ultrafast nonlinear optical devices, such as optical limiters and all-optical switchers. In this study, we present the wavelength-dependent coefficients of two-photon absorption (2PA) and three-photon absorption (3PA) in a GaS film across a broad range of wavelengths from 540 to 1600 nm. The observed dispersions in the 2PA and 3PA coefficients align well with the widely used two-band approximation model applied to direct bandgap semiconductors. Notably, the GaS film exhibits exceptional MPA properties with a maximum 2PA coefficient of 19.89 cm/GW at 620 nm and a maximum 3PA coefficient of 4.88 cm3/GW2 at 1500 nm. The GaS film surpasses those found in traditional wide-bandgap semiconductors like β-Ga2O3, GaN, ZnO, and ZnS while remaining comparable to monolayer MoS2, CsPbBr3, and (C4H9NH3)2PbBr4 perovskites. By employing a simplified two-energy-level model analysis, our results indicate that these large MPA coefficients are primarily determined by the remarkable absorption cross sections, which are approximately 4.82 × 10-52·cm4·s·photon-1 at 620 nm for 2PA and 8.17 × 10-80·cm6·s2·photon-2 at 1500 nm for 3PA. Our findings demonstrate significant potential for utilizing GaS films in nonlinear optical applications.
Chinese Optics Letters
- Publication Date: Feb. 04, 2025
- Vol. 23, Issue 1, 011901 (2025)
Observation of optical rogue waves in 2D optical lattice
Meng Li, Jie Song, Fuqiang Li, and Cibo Lou
We use a broad Gaussian beam with perturbations to motivate rogue waves (RWs) in a two-dimensional optical-induced lattice. In a linear situation, we fail to observe RWs. Nevertheless, under a nonlinear condition, the probability of RWs in the lattice is less than that in a homogeneous medium. Additionally, we obtain a shorter long-tail distribution of probability density function in an optical lattice. We use a broad Gaussian beam with perturbations to motivate rogue waves (RWs) in a two-dimensional optical-induced lattice. In a linear situation, we fail to observe RWs. Nevertheless, under a nonlinear condition, the probability of RWs in the lattice is less than that in a homogeneous medium. Additionally, we obtain a shorter long-tail distribution of probability density function in an optical lattice.
Chinese Optics Letters
- Publication Date: Jul. 29, 2024
- Vol. 22, Issue 7, 071903 (2024)
High-efficiency Brillouin lasing in a planar GeSbS spiral-ring resonator
Jingcui Song, Yuhang Wei, Chunxu Wang, Shuixian Yang, Yan Li, Tianhua Feng, Xiaojie Guo, and Zhaohui Li
Stimulated Brillouin scattering in planar integrated circuits promises to realize compact and highly coherent lasers. Here we report efficient Brillouin lasing at telecommunication wavelength from a planar Ge25Sb10S65 chalcogenide (ChG) resonator with a high quality factor above 106. A low lasing threshold of 24.8 mW is achieved with a slope efficiency of 8.3%. An 8-kHz linewidth is measured for 1.56-mW on-chip output power. This work offers a good opportunity to enrich the versatility and functionality of the ChG photonics on account of their intrinsic advantages of low loss, high third-order nonlinearity, and potential capacity for wafer-scale fabrication. Stimulated Brillouin scattering in planar integrated circuits promises to realize compact and highly coherent lasers. Here we report efficient Brillouin lasing at telecommunication wavelength from a planar Ge25Sb10S65 chalcogenide (ChG) resonator with a high quality factor above 106. A low lasing threshold of 24.8 mW is achieved with a slope efficiency of 8.3%. An 8-kHz linewidth is measured for 1.56-mW on-chip output power. This work offers a good opportunity to enrich the versatility and functionality of the ChG photonics on account of their intrinsic advantages of low loss, high third-order nonlinearity, and potential capacity for wafer-scale fabrication.
Chinese Optics Letters
- Publication Date: Jul. 16, 2024
- Vol. 22, Issue 7, 071902 (2024)
Wavelength-dependent nonlinear wavefront shaping in 3D nonlinear photonic crystal
Yunze Wang, Yan Sheng, Shan Liu, Ruwei Zhao, Tianxiang Xu, Tiefeng Xu, Feng Chen, and Wieslaw Krolikowski
A 3D nonlinear photonic crystal containing four parallel segments of periodic χ(2) grating structure is fabricated employing the femtosecond laser poling of ferroelectric Ca0.28Ba0.72Nb2O6 crystal. The second harmonic generation from this four-segment structure is studied with a fundamental Gaussian wave. By tuning the wavelength of the fundamental wave, the second harmonic varies from the Laguerre–Gaussian beam (topological charge lc = 1) to the higher-order Hermite–Gaussian beam and Laguerre–Gaussian again (lc = -1). This effect is caused by the wavelength-dependent phase delays introduced by the four-grating structure. Our study contributes to a deeper understanding of nonlinear wave interactions in 3D nonlinear photonic crystals. It also offers new possibilities for special beam generation at new frequencies and their control. A 3D nonlinear photonic crystal containing four parallel segments of periodic χ(2) grating structure is fabricated employing the femtosecond laser poling of ferroelectric Ca0.28Ba0.72Nb2O6 crystal. The second harmonic generation from this four-segment structure is studied with a fundamental Gaussian wave. By tuning the wavelength of the fundamental wave, the second harmonic varies from the Laguerre–Gaussian beam (topological charge lc = 1) to the higher-order Hermite–Gaussian beam and Laguerre–Gaussian again (lc = -1). This effect is caused by the wavelength-dependent phase delays introduced by the four-grating structure. Our study contributes to a deeper understanding of nonlinear wave interactions in 3D nonlinear photonic crystals. It also offers new possibilities for special beam generation at new frequencies and their control.
Chinese Optics Letters
- Publication Date: May. 28, 2024
- Vol. 22, Issue 7, 071901 (2024)
Generation of 160 nm vacuum ultraviolet light at 82 MHz in a KBBF crystal by the fifth-harmonic of a Ti:sapphire laser
Yun Zhang, and Lirong Wang
We report the generation of quasi-cw vacuum ultraviolet (VUV) light at 160 nm with a repetition rate of 82 MHz by two second-harmonic generations and one sum frequency mixing. The VUV laser light is produced as a fifth-harmonic generation of a mode-locked ps Ti:sapphire laser system by successive stages with nonlinear crystals of LBO and KBBF. A stable generation of laser light at 200 nm for more than 6 h is the most important step for obtaining the generation of light at a wavelength of 160 nm. We report the generation of quasi-cw vacuum ultraviolet (VUV) light at 160 nm with a repetition rate of 82 MHz by two second-harmonic generations and one sum frequency mixing. The VUV laser light is produced as a fifth-harmonic generation of a mode-locked ps Ti:sapphire laser system by successive stages with nonlinear crystals of LBO and KBBF. A stable generation of laser light at 200 nm for more than 6 h is the most important step for obtaining the generation of light at a wavelength of 160 nm.
Chinese Optics Letters
- Publication Date: May. 17, 2024
- Vol. 22, Issue 5, 051901 (2024)
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