Pump tuned wide tunable noncritically phase-matched ZnGeP2 narrow line width optical parametric oscillator

A line tunable singly resonant noncritically phase matched narrow band width ZnGeP₂ (ZGP) optical parametric oscillator pumped by the output idler radiation from a KTA OPO based on a 20 mm long KTA crystal pumped from a Q-switched Gaussian shaped Nd:YAG laser beam with a grating having grooves density 85 lines/mm has been demonstrated in the spectral ranges of 3–7 μm. The measured threshold of oscillation energy was 10 μJ. The conversion efficiency was 20.5% and slope efficiency of the ZGP OPO was 20% using a 23 mm long ZGP crystal at 26 mm cavity length. Line width of the generated infrared radiation from ZGP OPO was 37–60 nm.     

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.     

High-average-power mid-infrared ZnGeP2 optical parametric oscillator with a wavelength-dependent polarization rotator

A wavelength-dependent polarization rotator is used to transform the orthogonal polarizations of the signal and idler of a near-degenerate type II KTP optical parametric oscillator (OPO) into a common polarization state. This common polarization allows a single ZnGeP2 OPO to fully utilize the 2 microm signal and idler KTP OPO outputs in a mid-IR conversion. The simple design of the wavelength-dependent polarization rotator yields a compact source that simultaneously generates four mid-JR wavelengths collinearly with a total mid-IR average power of 5.5 W at a >15 kHz pulse repetition rate.     

ZnGeP2 optical parametric oscillator with 3.8-12.4-mum tunability

A ZnGeP>(2) (ZGP) optical parametric oscillator (OPO) with wide mid-IR tunability has been demonstrated. The singly resonant angle-tuned ZGP OPO was pumped by 100-ns erbium laser pulses at lambda =2.93mum and yielded output that was continuously tunable from 3.8 to 12.4 mum (type I phase matching) and from 4 to 10 mum (type II phase matching). An OPO pump threshold was less than 1 mJ in the whole 4-12 mum range of the output, and the quantum conversion efficiency reached 35%. An OPO linewidth was typically a few wave numbers; however, with a single intracavity etalon (uncoated Si plate) in a type II OPO it was narrowed to <0.5cm(-1). We demonstrate the sensitive detection of N(2)O gas with the narrow-linewidth OPO.     

Continuous wave tunable fiber optical parametric oscillator with double-pass pump configuration

We demonstrate a continuous wave tunable fiber optical parametric oscillator in a Fabry–Perot cavity consisting of a 500-m highly nonlinear fiber. In this work, the pump propagates in both directions together with the signal, thus making full use of its parametric gain. The resultant laser peak power is uneven across the wavelength range of interest due to wavelength-dependent phase modulation by the single-mode fiber sections in the cavity. This can be solved by filtering the idler spectral component from the oscillating cavity.     

Broadly tunable femtosecond parametric oscillator using a photonic crystal fiber

Pulses as short as 460 fs and a tuning range as wide as 200 nm around 1 microm have been achieved from a photonic-crystal-fiber-based parametric oscillator. The ring cavity with only 65 cm of photonic crystal fiber is synchronously pumped with a tunable passively mode-locked Yb-doped fiber laser. Widely extended tunability is achieved by using the modulation instability gain in normal dispersion as the result of high-order dispersion in the photonic crystal fiber.     

Broadly tunable mid-infrared femtosecond optical parametric oscillator using all-solid-state-pumped periodically poled lithium niobate

We describe a high-repetition-rate femtosecond optical parametric oscillator (OPO) that was broadly tunable in the mid infrared. The all-solid-state-pumped OPO was based on quasi-phase matching in periodically poled lithium niobate. The idler was tunable from approximately 1.7 mum to beyond 5.4 mum, with maximum average power levels greater than 200 mW and more than 20 mW of average power at 5.4 mum. We used interferometric autocorrelation to characterize the mid-infrared idler pulses, which typically had durations of 125 fs. This OPO had a pumping threshold as low as 65 mW of average pump power, a maximum conversion efficiency of >35% into the near-infrared signal, a slope efficiency for the signal of approximately 60%, and a maximum pump depletion of more than 85%.     

ZnGeP2 parametric oscillator pumped by a linewidth-narrowed parametric 2 microm source

A tandem optical parametric oscillator (OPO) is used to convert radiation from 1.064 microm to the mid-infrared. Spectral bandwidth narrowing close to 80 times compared with a conventional cavity was achieved by using a bulk Bragg grating as an outcoupler in a near-degenerate periodically poled KTiOPO(4) OPO. The narrowed 2,008 nm radiation was subsequently used for pumping the ZnGeP(2) OPO, which was tunable between 3.3 and 5.2 microm. Pulse energies of 170 microJ and pump depletion close to 70% were obtained in the ZnGeP(2) OPO. To our knowledge this is the first time the output from a near-degenerate type I PPKTP OPO has been used for ZnGeP(2) OPO pumping.     

Broadly tunable infrared femtosecond optical parametric oscillator based on periodically poled RbTiOAsO(4)

We present results from what we believe is the first reported example of an optical parametric oscillator based on periodically poled RbTiOAsO(4). The oscillator is pumped by a femtosecond self-mode-locked Ti:sapphire laser and, with a single-grating 2-mm-long crystal and one mirror set, a combination of pump and cavity-length tuning provided wavelength coverage from 1060 to 1225nm (signal) and 2.67 to 4.5 microm (idler). Average output powers were as much as 120mW in the signal and 105mW in the idler and interferometric autocorrelations recorded at signal and idler wavelengths of 1.1 and 3.26 microm, respectively, imply pulse durations of 125 and 115fs, respectively.     

A ring ZnGeP2 optical parametric oscillator pumped by a Ho:LuAG laser

We have demonstrated that we believe to be the first ring ZnGeP₂ (ZGP) optical parametric oscillator (OPO) pumped by a pulsed Ho:LuAG laser. The maximum output power of the ring ZGP OPO laser was 5.51 W at 13.1 W incident Ho pump power, corresponding to a slope efficiency of 59.0 %. The ZGP OPO laser produced 14 ns mid-infrared pulses in the 3.72–4.01 and 4.37–4.75 μm spectral regions simultaneously. In addition, the continuous wave Ho:LuAG laser generated 26.5 W of linearly output at 2,094.4 nm at the absorbed Tm pump power of 49.9 W.     

Widely tunable single-frequency pulsed optical parametric oscillator

The spectral output of a nanosecond dual-cavity doubly resonant optical parametric oscillator has been investigated versus the relative length of the signal and idler cavities. Regions of stable single-frequency operation are determined by use of a type II phase-matched KTP crystal and compared with the predictions of a mode-overlap model. A wide mode-hop-free tuning range is obtained over 40 GHz, limited only by piezoelectric biases. Furthermore, discrete tuning is investigated over the full parametric gain curve. For demonstration purposes, experiments are performed in the domain that is most inclined to multifrequency emission, i.e., near degeneracy.     

Widely tunable femtosecond fiber optical parametric oscillator

The phase-matching condition in a fiber is discussed. A balance among the different orders of fiber dispersion can be found to achieve a widely tuning modulation instability gain for pumping around the normal dispersion regime. Three coupled nonlinear wave equations are used to simulate the femtosecond fiber optical parametric oscillator. The numerical results show that, through appropriate choice of dispersion, femtosecond pulses with a 180-nm tunable range can be generated when pump wavelength near a fiber’s zero-dispersion wavelength is tuned only 7 nm. Further tuning is limited by the walk-off between the pump and the signal pulses.     

Widely tunable optical parametric oscillator with electrical wavelength control

A LiNbO(3) optical parametric oscillator (OPO) pumped at 930nm shows a wide phase-matching curve. Each pulse produced by the OPO has a very broad natural linewidth, from 1480 to 1800 nm for the signal and from 1950 to 2550 nm for the idler. The emission wavelength is controlled thanks to an electrically tunable Fabry-Perot interferometer inserted into the OPO cavity. The signal wavelength is electrically tuned in the range 1450-1850nm without crystal rotation.     

Theoretical analysis of self-phase locking in a type II phase-matched optical parametric oscillator

We analyze a doubly-resonant type II phase-matched optical parametric oscillator that includes an intracavity waveplate for inducing mutual injection locking between the signal and the idler. The intracavity waveplate provides a linear coupling between the normally orthogonally polarized signal and idler fields and allows for mode locking at frequency degeneracy. Under mode locked conditions the signal–idler phase difference is locked and the optical parametric oscillator becomes self-phase locked. The signal–idler phase can be adjusted by changing the operating point within the locking range. Two self-phase locked modes with different thresholds and signal–idler phases are possible. Characteristics of the self-phase locked regime are presented for different linear coupling strengths.     

宽调谐高效率的BBO光参量振荡器

本文报道用354.7nm泵浦的单共振BBO脉冲光参量振荡器在413～661nm和2513～765nm波段内获得了可调谐的振荡输出,最高总能量转换效率达52％;文中还讨论了输出特性。     

Narrowband and tunable ring optical parametric oscillator with a volume Bragg grating

We demonstrate a tunable nanosecond optical parametric oscillator with a narrowed signal spectrum. This was done by use of a volume Bragg grating based retroreflector, which makes the tuning simple and yields a compact design. Using periodically poled KTiOPO4 as the nonlinear medium, we generated 0.42 mJ of signal energy at 760 nm with a tuning range of 5 nm(2.6 THz) and a bandwidth of 0.25 nm(130 GHz) when the oscillator was pumped at 532 nm with 1.3 mJ of energy.     

可调谐PPLN中红外光参量振荡器失调特性

 通过对晶体进行周期调谐,实现了中红外参量光输出,在此基础上研究了晶体移动、腔镜偏转等对失调特性的影响。结果表明：由于PPLN通道的小尺寸波导特性和参量振荡特性,其失调特性不同于常规激光器。PPLN晶体沿不同轴移动的功率变化曲线有不同的特点,沿x轴移动的失调容限大于沿y轴移动的失调容限;腔镜的失调容限与腔镜偏转方向有关,腔镜横向偏转的失调容限大于纵向偏转的失调容限;PPLN晶体温度和通道对失调容限几乎没有影响。     

Rapidly tunable continuous-wave optical parametric oscillator pumped by a fiber laser

We report on rapid, all-electronically controlled wavelength tuning of a continuous-wave (cw) optical parametric oscillator (OPO) pumped by an ytterbium fiber laser. The OPO is singly resonant for the signal wave and consists of a 40-mm-long periodically poled lithium niobate crystal in a four-mirror ring cavity. By tuning of the fiber-laser wavelength over 33 nm through an intracavity acousto-optic tunable filter, the OPO idler wavelength is tuned from 3160 to 3500 nm in 330 micros, corresponding to an idler frequency-tuning speed of 28 THz/ms. At a fiber-laser power of 6.6 W at 1074 nm, the singly resonant OPO generates 1.13-W cw idler radiation at 3200 nm.     

Mid-infrared tunable dual-wavelength generation based on a quasi-phase-matched optical parametric oscillator

We report an efficient optical parametric oscillator (OPO) of dual idler wave output based on periodically poled MgO:LiNbO₃ with a periodically-phase-reversed grating structure, which is pumped by a Q-switched 1.064 μm laser with a repetition rate of 50 kHz. 0.98 W of dual idler-waves at 3.824 μm and 3.731 μm is achieved at room temperature, leading to a 12.9% conversion efficiency. The crystal temperature tuning provides output tunability of the dual idler wavelengths. In addition, the sum frequency generation of the dual signal waves is simultaneously observed in the OPO cavity.     

Multiwatt level output powers from a tunable fiber optical parametric oscillator

We present an all-fiber high average power fiber optical parametric oscillator based on standard telecommunications dispersion-shifted fiber. The output of the oscillator is continuously tunable out to ±28 THz from the pump wavelength. The average power of the oscillator's output is in excess of 1.9?W in each sideband out to ±25 THz detuning. Between 5 and 14 THz detuning, the average power of the Stokes output is in excess of 3.8 W.