Realizing high efficiency 532 nm laser by optimizing the mode- and impedance-matching

Yao, Wenxiu; Wang, Qingwei; Liang, Tian; Li, Ruixin; Shi, Shengli; Wang, JinRong; Wang, Yajun; Zheng, Yaohui

doi:10.1088/1612-202x/abd23d

Cited by 3 publications

(1 citation statement)

References 44 publications

(47 reference statements)

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“…second harmonic generation. [6,7] Ideally, the power spectrum density (PSD) of the second harmonic relative intensity noise (RIN) is 6 dB higher than that of the fundamental. [8] In this paper, we show that in a cavity enhanced SHG pumped by a diode laser can exhibit RIN much higher than 6 dB.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the sideband noise of a cavity-enhanced second harmonic generator

Wang,

Shen,

Tang

et al. 2024

International Conference on Optics and Machine Vision (ICOMV 2024)

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Narrow linewidth ultraviolet (UV) lasers are widely used in high-resolution spectroscopy. Due to the limitation of gain materials, UV lasers are usually generated via optical nonlinear process. In this paper, the noise characteristics of UV lasers generated in a cavity-enhanced second harmonic generator (SHG) is studied both theoretically and experimentally. Evolution of the laser noise is calculated with the noise ellipse rotation model. Due to the interaction with the optical cavity, noise of the two quadratures of the input field are intercoupled. Therefore, the power spectrum density (PSD) of the generated second harmonic can significantly deviate from that of the fundamental. This effect is verified by measuring the PSD of a 388 nm SHG pumped by a common diode laser. The results in this paper give an insight into the research of noise suppression for UV lasers.

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Section: Introductionmentioning

confidence: 99%

Characterization of the sideband noise of a cavity-enhanced second harmonic generator

Wang,

Shen,

Tang

et al. 2024

International Conference on Optics and Machine Vision (ICOMV 2024)

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Manipulations and quantum tomography of bright squeezed states

Li¹,

Yao²,

Fan³

et al. 2021

Acta Phys. Sin.

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Generation and manipulation of continuous variable quantum states are the building blocks of quantum communication, quantum key distribution and quantum networks. According to the second-order nonlinear process of the periodically-poled potassium titanyl phosphate (PPKTP) crystal, we design a semi-monolithic optical parametric amplifier (OPA) cavity to generate the bright squeezed light at a wavelength of 1064 nm. With the injection of a seed beam, the squeezed state generated by the OPA has a coherent amplitude, so called bright squeezed state. The squeezing level is directly observed to be –11.6 dB when the pump power is 310 mW at an analysis frequency of 3 MHz. However, with the increase of the pump power, the purity of the squeezed state gets lower and lower due to the increased influence of the anti-squeezing quadrature component on the squeezed quadrature component in the detection process. To obtain a higher purity of the squeezed state for achieving linear optical manipulation and quantum tomography, we choose the pump power of 50 mW, the squeezing level decreases to –6 dB, and the purity of the squeezed state is 98.5% in this case. An electro-optic modulator is adopted to realize the liner manipulation of the squeezed light in the phase space. During the measurement of the bright squeezed state, all the data are taken on condition that the length of the OPA cavity and relative phase between the seed beam and the pump beam are locked by a locking loop. The direct current (DC) signal of the balanced homodyne detection (BHD) is used to accurately determine the phase corresponding to the time domain signal of the squeezed state, while the alternate current (AC) signal of the BHD is mixed with the signal generated by the function generator, after passing through a low-pass filter and a high-pass filter, the signal is then amplified by using a low-noise amplifier. A high-performance oscilloscope is finally used to simultaneously collect the signals, thus obtaining the quantum noise signal of the bright squeezed light after linear manipulation. Together with the maximum likelihood estimation algorithm, the quantum tomography, the density matrix and the Wigner function of the bright squeezed light are obtained, that is, all the information such as the photon number distribution of the quantum state is determined. Multiple iterations are taken in the maximum likelihood estimation algorithm process to eliminate the influence of the low quantum efficiency on the detection system, so that the density matrix is fitted well with the theoretical results.

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Influence of thermal lens effect on second harmonic process in semi-monolithic cavity scheme

Zhang¹,

Wang²,

Yao³

et al. 2022

Acta Phys. Sin.

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Second harmonic generation (SHG) is an effective way to generate short wavelength laser with high power. SHG is accompanied by absorptions of fundamental waves and harmonic waves, which make a fraction of the two waves deposit energy as heat and cause a temperature gradient along the radial direction of the periodically poled potassium titanyl phosphate (PPKTP) crystal. The inhomogeneous temperature distribution causes thermal lensing in the crystal. The thermal lensing effect will deform the spatial mode of the SHG cavity and result in the mode-mismatching of the fundamental wave to the SHG cavity, and the conversion efficiency of SHG process is so reduced. Moreover, with the increase of injected fundamental wave power, the influence caused by thermal lens becomes more and more serious. In order to obtain a high-efficiency frequency conversion, it is necessary to take measures to minimize the effect caused by thermal lensing. In this paper, we report on a high efficiency generation of green laser at 532 nm by external cavity SHG process with a semi-monolithic standing cavity. The influence of thermal lens effect on the optimal conversion efficiency in different semi-monolithic cavities was theoretically analyzed. The variation of conversion efficiency with the pump power in "plane-concave" semi-monolithic cavity based on parallel crystal and "concave-concave" semi-monolithic cavity based on concave crystal was quantitatively analyzed. In experiments, two types of cavity structures were built to measure the variation of frequency doubling conversion efficiency with pump power. For the "plane-concave" semi-monolithic cavity, the maximum green laser power of 747 mW was obtained and the corresponding conversion efficiency reaches (93.43)%, with injecting of 800 mW infrared laser. For the "concave-concave" semi-monolithic cavity, the maximum green laser power of 529 mW was obtained and the corresponding conversion efficiency is (88.23)%, with injecting of 600 mW infrared laser. The results show that the thermal lens impacts on the optimal conversion efficiency more serious in "concave-concave" semi-monolithic cavity in comparing with "plane-concave" semi-monolithic cavity. What's more, the influence of thermal lens effect gets higher and higher with the increase of the loss in the cavity. It is obviously that the "plane-concave" semi-monolithic cavity is more suitable for the SHG process and has huge potential in quantum optics and cold atom physics and provides a guide for future research on high-efficiency SHG process.

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Realizing high efficiency 532 nm laser by optimizing the mode- and impedance-matching

Cited by 3 publications

References 44 publications

Characterization of the sideband noise of a cavity-enhanced second harmonic generator

Characterization of the sideband noise of a cavity-enhanced second harmonic generator

Manipulations and quantum tomography of bright squeezed states

Influence of thermal lens effect on second harmonic process in semi-monolithic cavity scheme

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