Low-Threshold Mid-Infrared Optical Parametric Oscillator Using Periodically Poled LiNbO33

We report the generation of tunable mid-infrared optical pulses using all-solid-state pumped optical parametri coscillator in a periodically poled lithium niobate. Several ways were used to lower the threshold, resulting in a mean threshold as low as 6.5mW and an achievement of wavelength conversion in the 2.77-4.04μm spectral range. Continuous tuning range from 2.97 to 3.25μm was achieved. The maximum idler output power of 466mW at the wavelength of 3.41μm was obtained, which represents an optical-to-optical conversion efficiency of 19% from incident pump power to the idler output.     

Continuous-wave, single-frequency intracavity singly resonant optical parametric oscillator at 1.5-μm wavelength

We present a 1.5μm continuous-wave （CW） single-frequency intracavity singly resonant optical parametric oscillator （SRO） based on periodically poled lithium niobate （PPLN）. The SRO is placed inside the ring cavity of a single-frequency 1.06μm Nd：YVO4 laser pumped by a laser diode. The device delivers a maximum single-frequency output power of 310 mW at a resonant signal wavelength of 1.57 μm. The signal wave could be tuned from 1.57 to 1.59 μm by temperature tuning of PPLN crystal over the range of 130 - 170℃.     

Periodically poled lithium niobate whispering gallery mode microcavities on a chip

In this study, we investigate the fabrication of periodically poled lithium niobate(PPLN) microdisk cavities on a chip. These resonators are fabricated from a PPLN film with a 16 μm poling period on insulator using conventional microfabrication techniques.The quality factor of the PPLN microdisk resonators with a 40-μm radius and a 700-nm thickness is 6.7×10~5. Second harmonic generation(SHG) with an efficiency of 2.2×10~(-6) mW(-1) is demonstrated in the fabricated PPLN microdisks. The nonlinear conversion efficiency could be considerably enhanced by optimizing the period and pattern of the poled structure and by improving the cavity quality factors.     

A Low-Pump-Threshold High-Repetition-Rate Intracavity Optical Parametric Generator Based on Periodically Poled Lithium Niobate

A low-pump-threshold high-repetition-rate intracavity optical parametric generator （IOPG） by using a periodically poled lithium niobate （PPLN） is reported. The PPLN, which is 18.7mm long and has a grating period of 28.93tzm at room temperature, is inserted in a diode-end-pumped Nd：YV04 laser with an acousto-optic Q switch. The parametric generation threshold is 1.3 W （diode laser power） at a Q-switch repetition rate of 19 kHz. At an incident diode pump power of 5 W, an average signal output power of 280mW has been achieved. The signal pulse duration is approximately 85 ns. By changing the crystal temperature from 120℃ to 250℃, the signal wavelength can be tuned from 1.493μm to 1.538μm.     

Mid-infrared generation based on a periodically poled LiNbO3 optical parametric oscillator

We report a nanosecond Nd:YVO_4-pumped optical parametric oscillator (OPO) based on periodically poled LiNbO_3 (PPLN). Tuning is achieved in this experiment by varying the temperature and period of the PPLN. The design of double-pass singly resonant oscillator (DSRO) and confocal cavity enables the OPO threshold to be lowered considerably, resulting in a simple, compact, all-solid-state configuration with the mid-infrared idler powers of up to 466mW at 3.41μm.     

Spectral Broadening in a Polarization-Maintaining Photonic Crystal Fibre by Femtosecond Pulses from an Optical Parametric Amplifier

The spectral broadening with the bandwidth of 83nm (1.2486-1.3318μm) in the 1.3μm region is achieved in a 0.2-m-long, polarization-maintaining photonic crystal fibre (PCF) with an average core radius of 1.8 μm, pumped by optical pulses at the wavelength 1.269μm, with the duration 25ors and the repetition rate 250kHz from an optical parametric amplifier. The polarization characteristics of the output spectra are also investigated.     

Low-threshold, high-efficiency, high-repetition-rate optical parametric generator based on periodically poled LiNbO3

We report a high-repetition-rate optical parametric generator (OPG) with a periodically poled lithium niobate (PPLN) crystal pumped by an acousto-optically Q-switched CW-diode-end-pumped Nd:YVO_4 laser. For the maximum 1064nm pump power of 970mW, the maximum conversion efficiency is 32.9% under the conditions of 250℃, 1064nm pulse repetition rate of 22.6kHz and pulse width of 12ns, and the PPLN OPG threshold in the collinear case is less than 23.7μJ. The output power increases with the increase of the crystal temperature. The 1485－1553nm signal wave and 3383－3754nm idler wave are obtained by changing the temperature and the angle of the PPLN crystal.     

High-Average-Power Nanosecond Quasi-Phase-Matched Single-Pass Optical Parametric Generator in Periodically Poled Lithium Niobate

A pulsed nanosecond optical parametric generator (OPG) in periodically poled lithium niobate (PPLN) crysal is presented. The pump laser is an acousto-optically Q-switched Nd:YVO4 laser with the maximum average power of 6.58 W. When the repetition rate is 50kHz and the pulse width of the pump source is 80ns, the maximum average total output power of the single-pass PPLN OPG is about 1.9 W, which includes 1.322 W of 1.536μm signal radiation. The length of the PPLN crystal is only 38.7mm (at room temperature) with a grating period of 28.93μm (at room temperature). The 1.502-1.536μm signal radiation and 3.652-3.465μm idler radiation are obtained by adjusting the PPLN crystal temperature from 155℃ to 250℃.     

Single-mode and tunable VCSELs in the near-to mid-infrared Invited Paper

Single-mode,long-wavelength vertical-cavity surface-emitting lasers(VCSELs)in the near-to mid-infrared covering the wavelength range from 1.3 to 2.3μm are presented.This wide spectral emission range opens applications in gas sensing and optical interconnects.All these lasers are monolithically grown in the InGaAlAs-InP material system utilizing a buried tunnel junction(BTJ)as current aperture.Fabricated with a novel high-speed design with reduced parasitics,bandwidths in excess of 10 GHz at 1.3 and 1.55μm have been achieved.Therefore,the coarse wavelength division multiplexing(CWDM)wavelength range of 1.3 to 1.6μm at 10 Gb/s can be accomplished with one technology.Error-free data-transmission at 10 Gb/s over a fiber link of 20 km is demonstrated.One-dimensional arrays have been fabricated with emission wavelengths addressable by current tuning.Micro-electro-mechanical system(MEMS)tunable devices provide an extended tuning range in excess of 50 nm with high spectral purity.All these devices feature continuous-wave(CW)operation with typical single-mode output powers exceeding 1 mW.The operation voltage is around 1-1.5 V and power consumption is as low as 10-20 mW.Furthermore,we have also developed VCSELs based on GaSb,targeting at the wavelength range from 2.3 to 3.0μm.The functionality of tunable diode laser spectroscopy(TDLS)systems is shown by presenting a laser hygrometer applying a 1.84-μm VCSEL.     

Generation of 170-fs Laser Pulses at 1053nm by a Passively Mode-Locked Yb:YAG Laser

A novel method is developed to obtain 1.05μm laser operation with a Yb：YAG laser. By using a Yb：YAG crystal with proper length and doping concentration, a femtosecond Yb： YAG laser is realized at the central wavelength of 1053nm. The measured pulse duration and spectral bandwidth （FWHM） are 170fs and 7nm; the repetition rate is 80 MHz. Under a power pump of 2 W, an average mode-locking power of 180mW is achieved.     

Low noise, continuous-wave single-frequency 1.5-μm laser generated by a singly resonant optical parametric oscillator

We report a low noise continuous-wave (CW) single-frequency 1.5-μm laser source obtained by a singly resonant optical parametric oscillator (SRO) based on periodically poled lithium niobate (PPLN). The SRO was pumped by a CW single-frequency Nd:YVO₄ laser at 1.06 μm. The 1.02 W of CW single-frequency signal laser at 1.5 μm was obtained at pump power of 6 W. At the output power of around 0.75 W, the power stability was better than ±1.5% and no mode-hopping was observed in 30 min and frequency stability was better than 8.5 MHz in 1 min. The signal wavelength could be tuned from 1.57 to 1.59 μm by varying the PPLN temperature. The 1.5-μm laser exhibits low noise characteristics, the intensity noise of the laser reaches the shot noise limit (SNL) at an analysis frequency of 4 MHz and the phase noise is less than 1 dB above the SNL at analysis frequencies above 10 MHz.     

CsPbBr_3 nanocrystal for mode-locking Tm-doped fiber laser

CsPbBr_3 nanocrystal is used as the saturable absorber(SA) for mode-locking Tm-doped fiber laser in a ring fiber cavity.The modulation depth, saturable intensity, and non-saturable loss of the fabricated SA are 14.1%, 2.5 MW/cm~2,and 5.9%, respectively.In the mode-locking operation, the mode-locked pulse train has a repetition rate of 16.6 MHz with pulse width of 24.2 ps.The laser wavelength is centered at 1992.9 nm with 3-dB spectrum width of 2.5 nm.The maximum output power is 110 mW with slope efficiency of 7.1%.Our experiment shows that CsPbBr_3 nanocrystal can be used as an efficient SA in the 2-μm wavelength region.     

Efficient Generation of Red and Blue Light in a Dual-Structure Periodically Poled LiTaO3 Crystal

We demonstrate the efficient generation of red light at 671nm and blue light at 447nm from a diode-pumped Q-switched 1342nm Nd: YVO4 laser together with a periodically poled LiTaO3 (PPLT) crystal. The sample used in this experiment is a dual-structure PPLT crystal with the period of 14.9μm for the second harmonic generation and that of 4.9μm for the third harmonic generation. The red and blue light, with the respective average power of 752 m W and 153 m W were obtained in a single path under an average fundamental power of 1.74 W, corresponding to the conversion efficiencies of 43.2% and 8.8%, respectively. These results indicate that the dual-structure PPLT can be used to construct a compact and efficient all-solid-state red-and-blue dual-wavelength laser.     

Single-mode and tunable VCSELs in the near- to mid-infraredInvited Paper

Single-mode, long-wavelength vertical-cavity surface-emitting lasers (VCSELs) in the near- to mid-infrared covering the wavelength range from 1.3 to 2.3μm are presented. This wide spectral emission range opens applications in gas sensing and optical interconnects. All these lasers are monolithically grown in the InGaA1As-InP material system utilizing a buried tunnel junction (BTJ) as current aperture. Fabricated with a novel high-speed design with reduced parasitics, bandwidths in excess of 10 GHz at 1.3 and 1.55 μm have been achieved. Therefore, the coarse wavelength division multiplexing (CWDM) wavelength range of 1.3 to 1.6 μm at 10 Gb/s can be accomplished with one technology. Error-free data-transmission at 10 Gb/s over a fiber link of 20 km is demonstrated. One-dimensional arrays have been fabricated with emission wavelengths addressable by current tuning. Micro-electro-mechanical system (MEMS) tunable devices provide an extended tuning range in excess of 50 nm with high spectral purity. All these devices feature continuous-wave (CW) operation with typical single-mode output powers exceeding 1 mW. The operation voltage is around 1 - 1.5 V and power consumption is as low as 10 - 20 mW. Furthermore, we have also developed VCSELs based on GaSb, targeting at the wavelength range from 2.3 to 3.0 μm. The functionality of tunable diode laser spectroscopy (TDLS) systems is shown by presenting a laser hygrometer applying a 1.84-μm VCSEL.     

Generation of Red Light Femtosecond Pulses from an Intra-Cavity Frequency-Doubled Cr^4＋： Forsterite Laser

We demonstrate the generation of red light femtosecond laser pulses from an intra-cavity frequency-doubled Cr^4＋ ：forsterite laser. An average output power of 75 mW is obtained at the central wavelength of 647nm with a pulse width of 55 fs by inserting a 500μm-thick BBO crystal in the laser cavity. The bandwidth of the spectrum of second harmonic pulses is 9 nm, corresponding to a time-bandwidth product of 0.355.     

ReSe_2 as a saturable absorber in a Tm-doped yttrium lithium fluoride(Tm:YLF) pulse laser

This study investigates the applicability of a few-layer structure ReSe2 as a saturable absorber(SA) for demonstrating a passively Q-switched pulse laser. The ReSe2 SA had a modulation depth of 6.86%. The Q-switched experiment was successful in delivering a maximum average output power of 180 mW at the wavelength of1906.5 nm. The optimal pulse train had a pulse width of 1.61 μs and a repetition rate of 28.78 kHz. The experiment results verify that the few-layer structure ReSe2 could behave as an excellent SA at all-solid-state lasers, increasing the selection of SAs at near 2 μm lasers.     

Single-mode and tunable VCSELs in the near- to mid-infrared

Single-mode, long-wavelength vertical-cavity surface-emitting lasers （VCSELs） in the near- to mid-infrared covering the wavelength range from 1.3 to 2.3 μm are presented. This wide spectral emission range opens applications in gas sensing and optical interconnects. All these lasers are monolithically grown in the InGaAlAs-InP material system utilizing a buried tunnel junction （BTJ） as current aperture. Fabricated with a novel high-speed design with reduced parasitics, bandwidths in excess of 10 GHz at 1.3 and 1.55 μm have been achieved. Therefore, the coarse wavelength division multiplexing （CWDM） wavelength range of 1.3 to 1.6 μm at 10 Gb/s can be accomplished with one technology. Error-free data-transmission at 10 Gb/s over a fiber link of 20 km is demonstrated. One-dimensional arrays have been fabricated with emission wavelengths addressable by current tuning. Micro-electro-mechanical system （MEMS） tunable devices provide an extended tuning range in excess of 50 nm with high spectral purity. All these devices feature continuous-wave （CW） operation with typical single-mode output powers exceeding 1 mW. The operation voltage is around 1 - 1.5 V and power consumption is as low as 10 - 20 mW. Furthermore, we have also developed VCSELs based on GaSb, targeting functionality of tunable diode laser spectroscopy （TDLS） applying a 1.84-μm VCSEL. at the wavelength range from 2.3 to 3.0 μm. The systems is shown by presenting a laser hygrometer     

Widely continuous-tunable 2.789-4.957 μm twin- MgO：PPLN cascaded optical parametric oscillator

An all-solid-state mid-infrared optical parametric oscillator with wide tunability by using two identical multi-grating periodically poled 5-mol.-% MgO-doped lithium niobate cascaded is reported. The pump laser is an acousto-optically Q-switched Nd：YAG laser with 150-ns pulse width at repetition rate of 10 kHz. Wide tunability from 2.789 to 4.957μm at the idler wavelength is achieved by varying the temperature from 40 to 200 ~C and translating the grating periods from 26 to 31 μm with a step of 0.5μm. When the incident pump average power is 8.15 W, the maximum idler output average power is 2.23 W at 3.344 μm and the optic-optic conversion efficiency is about 27.4%.     

Diode-pumped Kerr-lens mode-locked Ti: sapphire laser with broad wavelength tunability

We report a direct blue-diode-pumped wavelength tunable Kerr-lens mode-locked Ti: sapphire laser.Central wavelength tunability as broad as 89 nm(736–825 nm) is achieved by adjusting the insertion of the prism.Pulses as short as 17 fs are generated at a central wavelength of 736 nm with an average output power of 31 mW.The maximum output power is 46.8 mW at a central wavelength of 797 nm with a pulse duration of 46 fs.     

A novel radiant source for infrared calibration by using a grooved surface

A radiant source with a large aperture at 5-95 ℃ in the wavelength bands of 8-12μm for calibrating infrared imaging systems has been designed. The effective emissivity of its flat bottom with concentric V-grooves was evaluated by the Monte-Carlo method whose correctness was tested and accuracy was discussed. The structure of the source was completed by incorporating the simulation results with the blackbody cavity effect. The source was certificated via an optical measurement system. The source can provide a consistent radiant flux with temperature uniformity of ±0.1 ℃ over an area of diameter of φ80 mm.