Temperature-tunable nanosecond optical parametric oscillator based on periodically poled

We report a compact quasi-phase-matched optical parametric oscillator (OPO) using periodically poled MgO-doped LiNbO₃ with different grating periods. The OPO is pumped by a diode-pumped passively Q-switched Nd:YAG laser providing 4.8-ns pulses at 5.4-kHz repetition rate. The OPO generates signal and idler wavelengths tunable in the ranges of 1.5– and 2.8–, respectively, by changing the crystal temperature between room temperature and . The temperature-dependent Sellmeier equation for the extraordinary refractive index of MgO-doped LiNbO₃ is modified in the Mid-IR region, which gives an accurate prediction of the experimental temperature-tuning results. The linewidth of the signal wave is in the range of 0.5–1.0 nm without any controlling element.     

High-efficiency nanosecond optical parametric oscillator with the stable ring configuration

High stability nanosecond OPO operation at 1.57 μm was realized based on the type II non-critically phase-matched (NCPM) KTP crystal by utilizing a single frequency Nd:YAG master oscillator power amplifier (MOPA) laser as pump source. Energy conversion efficiency of 18.1% was demonstrated with single-pass ring cavity which was approximately two times more than that of critical ring cavity. The highest slope efficiency of 37.76% and maximum signal pulse energy of 3.1 mJ were attained with the output reflectivity of R = 50% at the pulse repetition frequency of 100 Hz. Experimental results reveal that the nanosecond OPO with ring stable configuration is a promising design to meet the need of IPDA’s transmitter.     

1.2 W中红外ZnGeP2光参量振荡器

报导了利用Tm,HoGdVO4激光器抽运双谐振ZnGeP2光参量振荡器实验研究.Tm(5%),Ho(0.5%)GdVO4晶体采用液氮制冷方式,工作在77 K温度条件下.以25 W波长为800 nm的光纤耦合激光二极管抽运,2 μm激光最大平均功率7 W,脉冲宽度小于30 ns, 脉冲重复频率5 kHz到20 kHz可调.非线性频率转换晶体ZnGeP2长15 mm,55?切割,OPO谐振腔为平平腔,腔长约25 mm.在5W的2 μm激光抽运下,脉冲重复频率10 kHz,实现了信号光3.7 μm及闲频光4.5 μm中红外激光输出,参量光脉冲宽度为15～17 ns,最大平均功率大于1.2 W,光-光转换效率为20%.测量参量光输出光束全宽度远场发散角4 mrad,光束质量M2因子小于3.     

Frequency-modulation-mode-locked optical parametric oscillator

We demonstrate a novel technique for the generation of mode-locked pulses from a continuous-wave (cw) optical parametric oscillator (OPO). The technique is based on the deployment of a phase modulator in combination with an antiresonant ring interferometer internal to a cw OPO, simultaneously providing spectral broadening and phase-to-amplitude feedback modulation. The scheme is implemented in a doubly-resonant cw OPO based on MgO:sPPLT, configured in a standing-wave cavity and pumped at 532 nm. With the phase modulator activated and the cavity length synchronized, a stable train of 800 ps pulses is generated at a repetition rate of 160 MHz. Using single-pass second harmonic generation (SHG) of the OPO output, we observe a four times enhancement in SHG compared with cw operation, confirming the real achievement of energy concentration as a result of mode-locked operation.     

Polarization-mixing optical parametric oscillator

We report the experimental realization of a new type of optical parametric oscillator in which oscillation is achieved by polarization rotation in a linear retarder, followed by nonlinear polarization mixing. The mixing is performed by a type II degenerate parametric downconversion in a periodically poled KTP crystal pumped by a 1064 nm pulsed Nd:YAG pump. A single, linearly polarized beam, precisely at the degenerate wavelength is generated. The output spectrum has a narrow linewidth (below the instrumentation bandwidth of 1 nm) and is highly stable with respect to variations in the crystal temperature.     

Non-collinear nanosecond optical parametric oscillator based on periodically poled LN with tilted domain walls

We report on a non-collinear, 1064 nm pumped, 10 kHz repetition rate ns-OPO which consists of a 13 mm long periodically poled lithium niobate (PPLN) crystal in a hemispherical optical cavity. The non-collinear phase-matching is achieved by tilting the domains by 60° with respect to the pump beam. This phase-matching avoids back conversion of signal and idler radiation into pump radiation and thus improves the spatial quality of the generated OPO radiation considerably. At a pump power of 5.5 W the OPO provided a conversion efficiency of up to 34%. The generated OPO pulses with a total power of up to 1.85 W were emitted in an almost diffraction limited beam with a M²-value of 1.1. The beam quality did not change when the pump power was varied in the range of 2–5 W. PACS 42.65.-k; 42.65.Yj     

Picosecond intracavity optical parametric oscillator

We present a novel technique to generate picosecond pulses at 1.57 microm with kilohertz repetition rates, using an intracavity optical parametric oscillator. With this device we were able to generate up to 120-mW average power at a repetition rate of 2.5 kHz.     

90% pump depletion and good beam quality in a pulse-injection-seeded nanosecond optical parametric oscillator

We measured 90% pump depletion in a singly resonant image-rotating nanosecond optical parametric oscillator that was pulse-injection seeded by a self-generated signal pulse. The oscillator was pumped by an 8 ns duration single-frequency 532 nm pulse from an injection-seeded Q-switched Nd:YAG laser and resonated an 803 nm signal. The pump and pulsed-seed beams had flat-topped spatial fluence profiles with diameters of approximately 6 mm, giving a cavity Fresnel number at 803 nm approaching 400. The beam cleanup effects of the image-rotating cavity produce a far-field signal spatial fluence profile with approximately 60% of its energy falling within the diffraction-limited spot size.     

Continuous-wave fiber optical parametric oscillator

We report continuous-wave operation of singly resonant fiber optical parametric oscillators. In a cavity formed by 100 m of highly nonlinear fiber and two fiber Bragg gratings, the pump power threshold was 240 mW; the output wavelength could be tuned over 80 nm by tuning of the pump. We also obtained an internal conversion efficiency of 30%, compared with the maximum theoretical value of 50%, by use of a 1-km-long cavity.     

Actively mode-locked optical parametric oscillator

We report on what we believe to be the first demonstration of active mode locking of an optical parametric oscillator. An acousto-optic modulator is inserted into a nearly degenerate (approximately 1064 nm) and doubly resonant optical parametric oscillator based on periodically poled LiNbO3 and pumped with the second harmonic of a quasi-continuous-wave single-frequency Nd:YAG laser. When the modulation frequency is matched to the free spectral range of the cavity (120 MHz), a pulsed regime is observed, with pulse durations as short as 700 ps.     

Phase-matched self-doubling optical parametric oscillator

We report a synchronously pumped intracavity frequency-doubled optical parametric oscillator that employs a single KTiOPO(4) crystal for both parametric generation and frequency doubling. Both nonlinear processes are phase matched for the same direction of propagation in the crystal. The parametric oscillator, pumped by a femtosecond Ti:sapphire laser at a wavelength of 745 nm, generates a green output beam at 540 nm with a 29% power conversion efficiency. Angle tuning in conjunction with pump wavelength tuning provides output tunability in the 530-585-nm range.     

Femtosecond fiber-feedback optical parametric oscillator

We demonstrate what is to our knowledge the first synchronously pumped high-gain optical parametric oscillator (OPO) with feedback through a single-mode fiber. This device generates 2.3-2.7 W of signal power in 700-900-fs pulses tunable in a wavelength range from 1429 to 1473 nm. The necessary high gain was obtained from a periodically poled LiTaO(3) crystal pumped with as much as 8.2 W of power at 1030 nm from a passively mode-locked Yb:YAG laser with 600-fs pulse duration and a 35-MHz repetition rate. The fiber-feedback OPO setup is compact because most of the resonator feedback path consists of a standard telecom fiber. Because of the high parametric gain, the fiber-feedback OPO is highly insensitive to intracavity losses. For the same reason, the synchronization of the cavity with the pump laser is not critical, so active stabilization of the cavity length is not required.     

Compact 21-W 2-mum intracavity optical parametric oscillator

We report on an intracavity optical parametric oscillator (OPO) placed within a compact diode-pumped Nd:YALO laser cavity. This OPO utilizes a pair of KTP crystals, which are diffusion bonded together in a walk-off-compensated configuration. We have generated up to 21.4 W of 2-mum radiation, operating in a few-kilohertz range.     

High-repetition-rate eyesafe intracavity optical parametric oscillator

Received: 15 December 1997/Revised version: 27 April 1998     

中红外光学参量振荡器技术进展

3~5μm中红外激光器在环境污染检测、医疗、工业等领域具有重要的应用价值。本文总结了基于ZnGeP_2、MgO∶PPLN晶体的光参量振荡器(OPO)的国内外发展现状,分析了其各自不同结构系统设计的优势和发展前景。指出高功率、小体积、轻重量的光学参量振荡器是未来重要发展方向,发展的技术核心是生长更大尺寸的中红外激光晶体以及研制更高性能指标的OPO泵浦源,并对中红外激光器的发展趋势进行了展望。     

磷锗锌光学参量振荡器技术研究

报道了一台高重复频率2 mm光学参量振荡器泵浦的磷锗锌光学参量振荡器。磷锗锌晶体(ZnGeP2,简称ZGP)采用Ⅰ类相位匹配方式,切割角度q为55°,f为0°,尺寸5.5 mm×6 mm×18 mm,在4.0 kHz重复频率下,当注入5.2 W的2 mm圆偏振光时,获得310 mW中红外输出,p偏振态2 mm到3～5 mm光-光转换效率12%。通过调节晶体的角度,实验获得ZGP光学参量振荡器的波长调谐曲线,在误差范围内与理论变化规律相符。     

磷锗锌光学参量振荡器技术研究

 报道了一台高重复频率2 mm光学参量振荡器泵浦的磷锗锌光学参量振荡器。磷锗锌晶体(ZnGeP₂,简称ZGP)采用Ⅰ类相位匹配方式,切割角度q为55°,f为0°,尺寸5.5 mm×6 mm×18 mm,在4.0 kHz重复频率下,当注入5.2 W的2 mm圆偏振光时,获得310 mW中红外输出,p偏振态2 mm到3～5 mm光-光转换效率12%。通过调节晶体的角度,实验获得ZGP光学参量振荡器的波长调谐曲线,在误差范围内与理论变化规律相符。     

高增益LiNbO3光参量振荡器

报道一台采用调Q红宝石激光器泵浦的高增益角度调谐LiNbO_3光参量振荡器.最大输出能量和转换效率分别高达50mJ/pulse和19%.该振荡器从1.1444μm到1.7652μm连续可调谐.     

High-average-power KTiOAsO4 optical parametric oscillator

Using noncritically phase-matched 1-cm(2) -aperture KTiOAsO(4) (KTA) crystals in an optical parametric oscillator (OPO), we have demonstrated a sustained average signal power of 33 W at 1534.7 nm. To our knowledge, this is the highest-average-power signal ever generated by an OPO. The pump source was a 100-Hz Q -switched 1064-nm Nd:YAG laser. Compared with that of the similar and more-common material KTiOPO>(4) , idler absorption in KTA is negligible, allowing high-power operation with minimal thermally induced refractive distortion in the OPO crystal.     

Near-infrared cavity-dumped femtosecond optical parametric oscillator

We demonstrate a high-energy near-infrared cavity-dumped femtosecond optical parametric oscillator (OPO) based on periodically poled lithium niobate. The laser generates 90 nJ pulses at a repetition rate of up to 1 MHz when synchronously pumped by 800 mW output from a femtosecond Ti:sapphire laser. The laser is broadly tunable from 1.0 to 1.5 microm in the signal branch, with a pulse duration of < 60 fs at 1.2 microm. High intracavity power is achieved by running the laser in the regime of positive group-velocity dispersion.