Lithium Niobate Optical Parametric Oscillator Research Articles

High power, widely tunable femtosecond MgO:PPLN optical parametric oscillator

We demonstrate a high power, widely tunable femtosecond MgO-doped periodically poled lithium niobate (MgO:PPLN) optical parametric oscillator (OPO) at 151 MHz, pumped by a Kerr-lens mode-locked Yb:KGW laser. With a maximum pump power of 7 W, the OPO is capable of delivering as high as 2.2 W of the signal centered around 1500 nm with tunable signal spectrum ranges of 1377 nm–1730 nm at an extraction efficiency of 31.4%, which exhibits a long-term passive power stability better than 0.71% rms over 4 h. The maximum idler bandwidths of 185 nm at 3613 nm are obtained across the idler tuning ranges of 2539 nm–4191 nm. By compensating intracavity dispersion, the signal has the shortest pulse duration of 170 fs at 1428 nm.

Ultralow-threshold thin-film lithium niobate optical parametric oscillator

Materials with strong second-order ( χ ( 2 ) ) optical nonlinearity, especially lithium niobate, play a critical role in building optical parametric oscillators (OPOs). However, chip-scale integration of low-loss χ ( 2 ) materials remains challenging and limits the threshold power of on-chip χ ( 2 ) OPO. Here we report an on-chip lithium niobate optical parametric oscillator at the telecom wavelengths using a quasi-phase-matched, high-quality microring resonator, whose threshold power ( ∼ 30 µ W ) is 400 times lower than that in previous χ ( 2 ) integrated photonics platforms. An on-chip power conversion efficiency of 11% is obtained from pump to signal and idler fields at a pump power of 93 µW. The OPO wavelength tuning is achieved by varying the pump frequency and chip temperature. With the lowest power threshold among all on-chip OPOs demonstrated so far, as well as advantages including high conversion efficiency, flexibility in quasi-phase-matching, and device scalability, the thin-film lithium niobate OPO opens new opportunities for chip-based tunable classical and quantum light sources and provides a potential platform for realizing photonic neural networks.

Narrow-band periodically poled lithium niobate nonresonant optical parametric oscillator.

We report on a narrowband, nonresonant periodically poled lithium niobate (PPLN) optical parametric oscillator using a volume Bragg grating (VBG) as the spectral narrowing element. Pumping by a Nd:YVO4 laser at 1.06μm, a maximum output power of 4.75W is achieved at a repetition rate of 20kHz for a conversion efficiency of 47.5%. Both signal and idler spectra are narrowed to less than 2nm, at good beam quality and stability.

Tunable 3 µm optical vortex parametric oscillator

We propose a tunable millijoule-level 3-µm vortex laser formed with a 1-µm ns vortex pulse-pumped quasi-phase matching MgO-doped periodically poled lithium niobate (MgO:PPLN) optical parametric oscillator with a singly resonant plane-parallel cavity configuration. The wavelength of the vortex output is tuned within the range of 3.360–3.677 µm merely by controlling the temperature of the MgO:PPLN crystal. The maximum vortex output energy of 2.14 mJ is obtained at the maximum pump energy of 21 mJ, and corresponds to an optical to optical conversion efficiency of 10.2% and a photon conversion efficiency of 33.5%. The handedness of the vortex output is controlled just by inverting the handedness of the pump vortex beam.

Highly efficient millijoule-level 3.5 µm MgO-doped periodically poled lithium niobate optical parametric oscillator

We report a millijoule-level mid-infrared MgO-doped periodically poled lithium niobate (MgO:PPLN) optical parametric oscillator pumped by a 1.064 µm nanosecond laser. The maximum mid-infrared 3.5 µm idler output energy reached 3.65 mJ at the pump energy of 21 mJ, corresponding to a photon conversion efficiency of 57%. The wavelength tunabilities of the signal and idler outputs were also realized, with the continuous tuning ranges of 1.501 to 1.558 µm and 3.650 to 3.353 µm, respectively, by controlling the temperature of the MgO:PPLN crystal. The beam quality factor (M2) of the mid-infrared idler output was measured to be <1.75.

High-power femtosecond mid-IR sources for s-SNOM applications

We demonstrate two high-power femtosecond mid-infrared (mid-IR) sources that can be combined with a scattering-type scanning near-field optical microscope (s-SNOM). The first one is based on difference frequency generation (DFG) between the two signal wavelengths of a high-power dual-signal-wavelength periodically poled lithium niobate (PPLN) optical parametric oscillator (OPO) and covers the spectral range from 10.5 μm to 16.5 μm. The second one is an AgGaSe2 OPO pumped by the PPLN OPO. With this mid-IR OPO we obtained up to 113 mW average idler power at 4857 nm with more than 40 cm−1 FWHM spectral width. We demonstrate mid-IR near-field spectra and near-field images that we obtained by combining the broadband femtosecond mid-IR DFG source with an s-SNOM.

A continuous-wave, widely tunable, intra-cavity, singly resonant, magnesium-doped, periodically poled lithium niobate optical parametric oscillator

We report a continuous-wave (CW), intra-cavity singly resonant optical parametric oscillator (OPO), based on periodically poled MgO:LiNbO3 pumped by a diode-end-pumped CW Nd:YVO4 laser, and calculate the gain of optical parametric amplification as a function of pump beam waist (at 1064 nm) in the singly resonant OPO (SRO) cavity, to balance the mode-matching and the intensity for the higher gain of a signal wave in the operation of the SRO. In order to achieve maximum gain, we use a convex lens to limit the 1064 nm beam waist. In the experiment, a tunable signal output from 1492 to 1614 nm and an idler output from 3122 to 3709 nm are obtained. For an 808 nm pump power of 11.5 W, a maximum signal output power of up to 2.48 W at 1586 nm and an idler output power of 1.1 W at 3232 nm are achieved with a total optical-to-optical conversion efficiency of 31%.

High-Resolution Sub-Doppler Lamb Dips of theν2Fundamental Band ofH3+

The high-resolution sub-Doppler Lamb dips of the ν2 fundamental band transitions of H3(+) have been observed using an extended negative glow discharge tube as an ion source and a periodically poled lithium niobate optical parametric oscillator as a radiation source. The absolute frequency of the R(1,0) transition was measured to be 81,720,371.550 MHz with an accuracy of 250 kHz using an optical frequency comb. In addition, we have investigated the linewidth of the Lamb-dip signal of the R(3,0) transition systematically and obtained its pressure-broadening parameter, which may shed some light on the reaction of H3(+) with H2. This is the first observation of the infrared saturated spectrum and the first determination of the pressure-broadening parameter of the ro-vibrational transitions of a molecular ion.

Absorption measurement of a 50-mm-Long periodically poled lithium niobate optical parametric oscillator pumped at 1064 nm by a Nd: YAG laser

We measured the absorption of different periodically poled lithium niobate crystals when different wavelength beams come through them. The choice of a periodically poled lithium niobate crystal is utilized by a singly resonant oscillator to efficiently generate 3800-nm light when it is pumped by a 1064-nm laser and to generate the 2600-nm signal, and, then, injection seeded at 1550 nm. The temperature-tuning curve and idler output power of the chosen crystal are measured.

Laser dazzling of infrared focal plane array cameras

Modern weapons systems often use infrared imaging for acquisition and tracking of targets. In the acquisition phase, the operator uses the system to detect the target and aim the weapon. In the tracking phase, the images from the camera are used to guide the weapon to the target. One possible method of protection against such imaging systems is laser dazzling. The intended effect is to deny the imager a clear view of the target by saturating the detector and consequently preventing the weapon from making a hit. The problem of locating the threat and pointing the laser at it is closely connected to the countermeasure effectiveness. This has been investigated particularly for specific applications such as directed infrared countermeasure (DIRCM) systems for aircraft self-protection. Another application is sniper detection, which uses the ‘cat’s-eye’ or retro-reflection effect, which occurs when a searching laser beam is directed at the visor of the rifle. We currently aim to use the retro-reflection effect in a wider range of applications for locating optics.1 The aim of our dazzling work is to quantify the effects of laser countermeasures on mid-wave infrared (MWIR) imaging to predict the decrease in the detection and pointing capabilities of weapons systems. Dazzling with a continuous or quasicontinuous pulsed laser causes a reversible saturation effect on the detector array. Most of the current MWIR lasers provide output power levels that do not exceed saturation levels for practical applications. Permanent damage effects require much higher irradiance levels at the camera front optics. This might be within reach at shorter ranges with these lasers, but is not addressed in our current research. In our experiments we used a periodically poled lithium niobate optical parametric oscillator (PPLN OPO) laser pumped by an Nd:YVO4 (yttrium orthovanadate) laser to generate a 3.9μm laser wavelength.2 Figure 1 presents images of a standard 256×320 indium antimonide (InSb) camera irradiated by Figure 1. Impact of increasing laser irradiance on the InSb camera image.

Difference frequency generation between the output waves of the PP-MgO:LN optical parametric oscillator

The difference frequency generation in the AgGaSe2 crystal between output waves of a periodically poled MgO doped lithium niobate (PP-MgO : LN) optical parametric oscillator (OPO) is described in this paper. The wavelength of the generated radiation is tunable from 6 to 13 µm with the average generated power in the range of several microwatts. The set-up allows a rapid tuning of the wavelength in the limited region of spectra without changing the temperature of the PP-MgO : LN crystal. A typical spectral linewidth of 5 cm-1 makes this source suitable for spectrometry of complex molecules under atmospheric conditions. The measured spectrum of the acetone vapour is presented to confirm this fact. Keywords: nonlinear optics, optical frequency converters, infrared sources

A coherent spectrophotometer based on a periodically poled lithium niobate optical parametric oscillator

We report the optimisation and characterisation of a periodically poled lithium niobate (PPLN) optical parametric oscillator (OPO) pumped by a diode-pumped, Q-switched multiaxial TEM00 mode Nd:YAG laser operated at 1064 nm. Total conversion efficiency exceeding 66% was achieved. This OPO is used in a coherent spectrophotometer for optical component characterisation.

Difference-frequency mixing of output waves from a periodically poled lithium niobate optical parametric oscillator in a GaSe crystal

We report on an optical parametric oscillator (OPO) based on periodically poled lithium niobate (PPLN) pumped by a Nd:YAG laser, and on extending its tuning range by difference-frequency mixing of OPO output waves in GaSe crystal. Maximum combined signal and idler pulse energy of 2.7 mJ and slope efficiency of 25% have been achieved. The tuning range is 1.71 to 1.98 mm for the signal wave and 2.81 to 2.30 mm for the idler wave, using a single set of mirrors. As an application of this PPLN OPO, the signal and the idler waves are difference-frequency- mixed in a GaSe crystal to produce tunable mid-IR from 4.35 to 14.25 mm. The efficiency of the mixing has been analyzed, considering the experimental results. © 2002 Society of Photo-Optical Instrumentation Engineers.

Photoacoustic measurement of methane concentrations with a compact pulsed optical parametric oscillator.

A pulsed periodically poled lithium niobate optical parametric oscillator operating in a cavity with a grazing-incidence grating configuration was used for sensitive and precise measurement of trace quantities of methane in nitrogen by photoacoustic spectroscopy with a novel differential photoacoustic detector. A sensitivity of 1.2 parts in 10(9) by volume of methane was obtained in direct calibration measurements (not extrapolated). With this apparatus, in situ measurement of the methane concentration in ambient air under atmospheric conditions was demonstrated.

Periodically poled lithium niobate optical parametric oscillator pumped at 0.532 μm and use of its output to produce tunable 4.6–8.3 μm in AgGaS 2 crystal

We report an efficient, near-IR, periodically poled lithium niobate optical parametric oscillator pumped at 0.532 μm by second harmonic of a Nd:YAG laser. To obtain wide tuning range a multigrating crystal is used. The signal and idler radiation are tunable from 0.82 to 0.93 μm and 1.51 to 1.24 μm , respectively, by changing grating period and varying crystal temperature. Maximum output energy obtained is 350 μJ/pulse , when pumped at 1.6 mJ/pulse frequency-doubled Nd:YAG laser. The idler output ranging from 1.38 to 1.22 μm is difference-frequency-mixed with 1.064 μm Nd:YAG beam in a AgGaS 2 crystal to produce tunable radiation in the range 4.6 to 8.3 μm .

Nano-Second Periodically Poled Lithium Niobate Optical Parametric Oscillator with Planar Cavity Mirrors

We investigated a high-output ower, periodically poled lithium niobate(PPLN) optical parametric oscillator(OPO) pumped by a Q-switched Nd:YAG laser. Given the low optical damage threshold and the limited aperture (0.5mm thick) of PPLN, we tried to maximize the signal output power in a linear cavity consisting of two flat mirrors with a loosely focused pump beam. It is found that this simple cavity structure allowed a robust OPO operation, which was not sensitive to alignment compared with the conventional ones using concave mirrors. A maximum energy of 100 $\mu$ J/pulse was achieved for the signal at 1.36 ${\mu}{\textrm}{m}$ , while the oscillation threshold was 0.3 mJ/pulse for the pump at 1064 nm.

Tunable twin beams generated by a type-I LNB OPO

We present a novel scheme to separate spatially twin beams generated by a type-I lithium niobate (LNB) optical parametric oscillator near frequency degeneracy. The system is based on a holographic diffraction grating acting as a beam splitter in a balanced detector. The fast and easy temperature tuning of LNB index of refraction allows an easy control of the twin-beam wavelength distance in a range of the order of ∼100 nm. We report correlation spectra measured for different twin-beam wavelength separations (15–60 nm) with a maximum noise reduction of 3.2 dB at 3.5 MHz. The described system exhibited a pump resonance stability longer than 6 h with infrared output power fluctuations within 4% around an average value of ≃2 mW in each beam. The measured oscillation threshold pump power was lower than 31 mW.

Temporal behavior of a high repetition rate infrared optical parametric oscillator based on periodically poled materials

The temporal behavior of a nanosecond pulsed singly resonant periodically poled lithium niobate optical parametric oscillator has been studied both theoretically and experimentally. Taking into account the cylindrical symmetry of the system, a numerical model based on the Hankel transform has been developed. Good agreement is obtained between experiment and simulation. Moreover, the computation time is reduced roughly by a factor of 60 compared to the usual simulation software.

Generation of bright squeezed light at 1.06 μm using cascaded nonlinearities in a triply resonant cw periodically-poled lithium niobate optical parametric oscillator

We have used an ultralow threshold continuous-wave optical parametric oscillator (OPO) to reduce the quantum fluctuations of the reflected pump beam below the shot noise limit. The OPO consisted of a triply resonant cavity containing a periodically poled lithium niobate crystal pumped by a Nd:YAG (yttrium aluminum garnets) laser and giving signal and idler wavelengths close to $2.12\ensuremath{\mu}\mathrm{m}$ and a threshold as low as $300\ensuremath{\mu}\mathrm{W}.$ We detected the quantum fluctuations of the pump beam reflected by the OPO using a slightly modified homodyne detection technique. The measured noise reduction was $30%$ (inferred noise reduction at the output of the OPO $38%).$

Practical Bessel beam pumping of periodically poled optical parametric oscillators

The pumping of periodically poled optical parametric oscillators (OPOs) by practically realizable Bessel beams is analysed. The effect of the deviation of practical Bessel beams from the ideal form is assessed, the influence of the particular structure of periodically poled materials is discussed, and the concept of phase-matching aperture is introduced. In a typical situation, the efficiency of a periodically poled lithium niobate OPO pumped by a practical Bessel beam has been measured; no efficiency advantage was found in comparison to the corresponding Gaussian beam pumped system or to that predicted by the standard Brosnan-Byer model.