Resonant Optical Parametric Oscillator Research Articles

Broadband frequency comb generation through cascaded quadratic nonlinearity in thin-film lithium niobate microresonators.

Broadband frequency comb generation through cascaded quadratic nonlinearity remains experimentally untapped in free-space cavities with bulk χ(2) materials mainly due to the high threshold power and restricted ability of dispersion engineering. Thin-film lithium niobate (LN) is a good platform for nonlinear optics due to the tight mode confinement in a nano-dimensional waveguide, the ease of dispersion engineering, large quadratic nonlinearities, and flexible phase matching via periodic poling. Here we demonstrate broadband frequency comb generation through dispersion engineering in a thin-film LN microresonator. Bandwidths of 150 nm (80 nm) and 25 nm (12 nm) for center wavelengths at 1560 and 780 nm are achieved, respectively, in a cavity-enhanced second-harmonic generation (doubly resonant optical parametric oscillator). Our demonstration paves the way for pure quadratic soliton generation, which is a great complement to dissipative Kerr soliton frequency combs for extended interesting nonlinear applications.

Synchronization of two indirectly coupled singly resonant optical parametric oscillators

We analyse a system of a singly resonant optical parametric oscillator for a second order nonlinear material. First, we show that the dynamics of the resonating cavity signal mode can be expressed by a Stuart–Landau oscillator, for a certain pumping powers close to the threshold. Second, we couple two optical parametric oscillators indirectly via a cold resonator. When the condition of a weak coupling is satisfied, the limit-cycle of each oscillator is unaltered, and the system is described by a coupled phase oscillator model (Kuramoto model), where a frequency synchronization of the two oscillators occurs at a critical coupling constant.

Study on Output Characteristics of High-Power Singly Resonant Optical Parametric Oscillator

Study on Output Characteristics of High-Power Singly Resonant Optical Parametric Oscillator

Dynamically tunable broadband output coupling of optical oscillators based on non-cyclic geometric phase mirror

We present a uniquely versatile and efficient mirror system capable of real-time fine-tuning in reflection and transmission properties across a broad wavelength range and at a high optical power. Leveraging the principles of the non-cyclic geometric phase (GP) acquired by the clockwise and counterclockwise beams of the Sagnac interferometer satisfying the anti-resonant condition on propagation through the quarter-wave plate, half-wave plate, and quarter-wave plate combination having fast axes oriented at 45° (fixed), θ (variable), and −45° (fixed) with respect to the vertical, respectively, our mirror system offers dynamic transmission control across 0–100% without the need for realignment. Notably, the GP-based mirror (GP-mirror) preserves the polarization state of the reflected beam, making it ideal for polarization-sensitive applications. The wavelength insensitivity of the GP enables seamless operation of the mirror across a wide wavelength range. As a proof-of-principle, we use the GP-mirror as the output coupler of a continuous-wave, green-pumped, doubly resonant optical parametric oscillator (DRO) based on a 30-mm-long MgO:sPPLT crystal and obtain stable operation at high powers over a wide wavelength tuning range. For a pump power of 5 W, the DRO provides an output power of 2.45 W at an extraction efficiency as high as 49% when operated at optimum output coupling. The DRO shows a maximum pump depletion of 89% and delivers an optimum output power across a tuning range ≥90 nm. The demonstrated concept offers a promising approach for advancing the capabilities and control of coherent optical sources tunable across different spectral regions and in all time scales from continuous-wave to ultrafast femtosecond domain.

Auto-pump-depleted stable single-longitudinal-mode 1.5 μm source with the assistance of SHG.

To realize a stable single-longitudinal-mode (SLM) 1550-nm light source for the generation of non-classical states, a ring auto-pump-depleted singly resonant optical parametric oscillator (SRO) with the assistance of second-harmonic-wave generation (SHG) is designed and built in this Letter. A magnesium oxide doped periodically polarized lithium niobate (MgO:PPLN) crystal and a lithium triborate (LBO) crystal are employed as the optical parametric downconversion (OPDC) and SHG crystals, respectively. Especially, the introduced SHG can firstly increase the loss difference between the lasing and non-lasing modes so that the dual-mode or multi-mode coupling in the achieved SRO can be effectively eliminated and the stable SLM operation is achieved. At the same time, the SHG will automatically adjust the output coupling efficiency of SRO, so as to achieve efficient conversion efficiency and auto-pump depletion of SRO. In addition, due to the SHG, it is easy to achieve the low-intensity noise multi-wavelength output for the stable SLM SRO. As a result, the output powers of the SLM 1550 nm and 775 nm are up to 4.05 W and 3.25 W, respectively, and the total optical conversion of the built SRO can achieve 45.58%. The presented method paves a way to develop a compact stable SLM multi-wavelength SRO, and the obtained SRO is further beneficial to develop compact continuous-variable non-classical light fields.

Widely tunable near-infrared optical parametric oscillator based on a 5%MgO:PPLN partial cylinder pumped at 1064 nm by a 1-kHz sub-nanosecond microchip laser.

We report the implementation of a singly resonant optical parametric oscillator using a 5%MgO:PPLN partial cylinder pumped by a sub-nanosecond microchip laser emitting 1064 nm at a repetition rate of 1 kHz. It is continuously tunable from 1410 nm up to 4330 nm by rotating the cylinder and a total energy of several microjoules is emitted with a beam quality factor M2 lower than 3.

Tunable femtosecond optical parametric oscillators resonating at 0.65-1.02 µm and 1.07-2.3 µm.

We present a singly resonant femtosecond optical parametric oscillator (OPO) cavity architecture supporting ultra-broadband wavelength tuning and efficient outcoupling of the generated optical pulses. Experimentally, we demonstrate an OPO with its oscillating wavelength tuned over 652-1017 nm and 1075-2289 nm, spanning nearly 1.8 octaves. This is, as far as we know, the widest resonant-wave tuning range obtained from a green-pumped OPO. We show that intracavity dispersion management is crucial for the stationary and single-band operation of such a broadband wavelength tuning system. This architecture is universal, and therefore can be extended to allow the oscillation and ultra-broadband tuning of OPOs at various spectral regions.

Transient dynamics in a common singly resonant optical parametric oscillator

The dynamics of a common optical parametric oscillator (OPO) is demonstrated for the first time with dispersive Fourier transform (DFT) technique. The singly resonant MgO:PPLN-based optical parametric oscillator is synchronously pumped with an Yb-doped fiber amplifier, and delivers a femtosecond signal wave with a spectrum tuned from 1284 to 1517 nm. Then a DFT device is built and the birth and extinction dynamics of the single- and dual-wavelength signal wave of the OPO is recorded. Compared with conventional mode-locked lasers, the dynamics evolution of the OPO is entirely attributed to the nonlinear effects in the nonlinear crystal different from the atomic transitions in the active media, which gives rise to novel features in the starting progress of the OPO. Furthermore, a new way of energy transfer is discovered for the first time during the evolution of dual-wavelength signal wave. The results are believed to provide a unique insight into evolution in OPOs and are instructive for in-depth understanding of OPO and other nonlinear devices and materials.

Infrared tunable 5%MgO:PPLN OPO pumped by a 1-kHz sub-nanosecond microchip laser

We built and studied a singly resonant optical parametric oscillator using a 5%MgO:PPLN partial cylinder pumped by a sub-nanosecond microlaser emitting 1064 nm at a repetition rate of 1kHz. It is continuously tunable from 1410 nm up to 4330 nm by rotating the cylinder and a total energy of several micro Joules is emitted with a beam quality factor M² lower than 3.

Theoretical Analysis of Continuous-Wave Mid-Infrared Optical Vortex Source Generated by Singly Resonant Optical Parametric Oscillator

Due to the important application in the study of vibrational circular dichroism and helical dichroism of chiral molecules, the tunable vortex beam at mid-infrared region has attracted increasing attention. Based on orbital angular momentum (OAM) conservation in nonlinear interactions, the vortex pumped singly resonant optical parametric oscillator (SRO) is recognized as a versatile source of coherent vortex radiation providing high power and broad wavelength coverage from a single device. However, the low parametric gain and high oscillation threshold under continuous wave (cw) pumping has so far been the most challenging factor in generating cw tunable vortex beams. To predict the output characteristic of vortex pumped SRO, a theoretical model describing the vortex pumped SRO is needed. In this study, the theoretical model describing the vortex pumped SRO is set up under collimated Gaussian beam approximation. Output characteristics of different SROs are simulated numerically. By proper selection of pump scheme (such as double-pass pumping scheme), the vortex pumped mid-infrared SRO can oscillate at a relatively low pump power. By controlling the gain (mode overlap ratio between the pump and resonant wave in the nonlinear crystal) and loss (employing a spot-defect mirror with different defect size as the output coupler) of the resonant signal mode in the SRO, the OAM of the pump beam can be directionally transferred to a specific down converted beam. The transfer mechanism of the OAM among the pump light and the down-converted beams and factors affecting the transfer are studied. Our study provides the guidelines for the design and optimization of vortex pumped SRO under cw operation.

Squeezing level strengthened by a temperature dependent dispersion compensation methodology

Doubly resonant optical parametric oscillator (DR-OPO) is a valuable resource for preparing squeezed state. Temperature dependent dispersion compensation technology has become a popular methodology for high degree squeezing generation with DR-OPO. Nevertheless, details for the realization of temperature dependent DR-OPO have not been demonstrated yet. Here, we have constructed a full experimental layout for charactering the doubly resonant temperatures and verifying the squeezing levels in the phase matching bandwidth of the crystal. Three co-resonance temperatures of 30.74 °C, 42.54 °C and 53.71 °C were directly measured, at which 11.7 dB, 12.3 dB and 11.5 dB squeezing were observed, respectively. The experimental and theoretical results both indicate that the temperature dependent frequency detuning contributes to the discrepancy of the squeezing levels for the three temperature conditions. Careful calibration of the temperature dependent frequency detuning should be tracked to strengthen the squeezing level with DR-OPO.

Optical parametric oscillator and amplifier providing tunable, narrowband nanosecond laser pulses in the mid-infrared with mJ pulse energy

We report on an all-solid-state light source for nanosecond (ns) laser pulses, with broad tunability in the mid-infrared, spectral bandwidth close to the Fourier transform limit, and pulse energy in the mJ regime. To this end, we extend a tunable, continuous wave (cw) singly resonant optical parametric oscillator by an optical parametric pre-amplifier with a periodically poled lithium niobate crystal and a power amplifier stage with two bulk lithium niobate crystals. We demonstrate pulse energies beyond 1 mJ in a tuning range between 3.3 and 3.8 upmu mathrm {m} center wavelength, with options for even larger output pulse energy and tuning range. The total conversion efficiency in the power amplifier reaches 20%. From measurements of absorption spectroscopy, we determine a very narrow linewidth of 108 MHz (full width at half maximum, FWHM), which is only a factor of 1.4 above the Fourier limit. We demonstrate the applicability and versatility of the laser system for nonlinear spectroscopy by resonantly enhanced third harmonic generation and sum frequency mixing in a gas sample of HCl molecules.

Stimulated polariton scattering in an Yb laser pumped lithium niobate based continuous-wave singly resonant optical parametric oscillator

The effective refractive index of a dielectric medium modifies in the infrared spectral band due to a significant contribution from the vibrational modes by virtue of the presence of heavy ions. The coupling between electromagnetic (EM) modes and transverse optical (TO) vibrational modes is the underlying principle behind such a modification. This interaction manifests through the generation of polariton modes that can be observed in the Raman spectrum. However, they do not coincide with the peaks associated with the Raman scattering process. In the present work, we show that the polariton modes can be excited in a lithium niobate based continuous-wave singly resonant optical parametric oscillator (SRO) pumped by a single-frequency, near-infrared Yb-doped fiber laser. The stimulated polariton scattering process is triggered by a strong interaction between the mid-infrared resonant SRO signal beam and TO phonon modes of a lithium niobate crystal, which leads to generation of Stokes mode(s). Such mode(s) can be observed as side peak(s) in the SRO signal spectrum. The generated low energy polariton mode exhibits a dominant EM character, and this provides a plausible route to generate narrow linewidth far-infrared (FIR) or terahertz radiation by utilizing the high intra-cavity signal power in the SRO. In addition, the off-axis FIR generation process assists in reducing the thermal load on the lithium niobate crystal at high pump powers.

Self-cascaded noncritically-phase-matched KTP optical parametric oscillator for generating orthogonally polarized multi-wavelength emissions at 3 μm

Mid-infrared self-cascaded noncritically-phase-matched (NCPM) KTP optical parametric oscillator (OPO) was developed, generating multiple wavelengths at 2.95, 3.29 and 3.37 μm. The polarization state of 2.95 μm is orthogonal to that of the other two wavelengths. Under 1064 nm intracavity pumping, the first NCPM KTP-OPO can generate signal and idler waves at 1.57 and 3.29 μm, respectively. Then the 1.57 μm is further used as pump light for the second NCPM OPO in the same KTP, generating signal and idler waves at 2.95 and 3.37 μm. Broadband spectral feedback condition is established between the OPO cavity mirrors, enabling the two NCPM OPOs to operate simultaneously in the same KTP and OPO resonator. With regard to 2.95 μm, the achieved maximum average output power and minimum pulse width are respectively 1.18 W and 5 ns, corresponding to a pulse peak power of 56.9 kW with 4.2 kHz repetition rate. As for the dual-wavelength at 3.29 and 3.37 μm, the maximum total average output power is 0.22 W. Our work provides an effective scheme to obtain multiple wavelength laser output in 3 μm region with orthogonal polarization state.

Watt-level, green-pumped optical parametric oscillator based on periodically poled potassium titanyl phosphate with high extraction efficiency

We report a compact, efficient optical parametric oscillator (OPO) based on a periodically poled potassium titanyl phosphate (PPKTP) crystal pumped by a 532 nm laser, which generated 1.51 W of average power at the signal wavelength of 709 nm with the pulse duration of ∼ 1.0 ns. The extraction efficiency was up to 59%. To the best of our knowledge, this is the first report on Watt-level green-pumped PPKTP-based singly resonant oscillator OPO (SRO-OPO). The precise build-up time of OPO was determined to be 1.6 ns benefitting from the characteristic of twin-peak pulse profile of pump beam. The spectrum width of the idler was also measured to be 4.2 nm with the central wavelength of 2134 nm at 0.2 nm spectral resolution of optical spectrum analyzer. In addition, the beam quality of M 2 < 1.9 of generated signal exhibits a good consistency with M 2 < 1.5 for the pump source.

Theoretical and experimental study on gain competition adjustment of intracavity pumped dual-wavelength optical parametric oscillator using an aperiodically poled lithium niobate at approximately 3.30 and 3.84 μm

An intracavity pumped dual-wavelength optical parametric oscillator based on a single MgO:APLN crystal at approximately 3.30 and 3.84 μm was studied using a folded-type double cavity, which consists of a 1.06 μm resonator and dual-wavelength optical parametric oscillator. With the maximum incident diode power of 43.84 W, the maximum output powers of 1.43 W at 3.30 μm and 2.47 W at 3.84 μm were obtained under T = 70%@1.57 μm and T = 25%@1.47 μm at a repetition rate of 40 kHz, corresponding to conversion efficiencies of 3.26% and 5.63%, respectively. The pulse widths of 11.35 ns at 3.30 μm and 13.17 ns at 3.84 μm were obtained synchronously. A dual-wavelength optical parametric energy conversion model was set up to simulate the influence of the transmittance at resonant signal wavelengths on the output power of idler wavelengths. Both theoretical and experimental results demonstrated that the relationships in output power between 3.30 and 3.84 μm can be affected by adjusting the transmittance at signal wavelengths.

Tunable short-wave near-infrared continuous wave source based on a 532 nm pumped singly resonant optical parametric idler oscillator

We report a continuous wave (CW) singly resonant optical parametric idler oscillator (i-SRO) capable of providing high power, high power conversion efficiency, widely tunable radiation in the short-wave near-infrared (NIR) range. The i-SRO is pumped by a fiber-laser-based laser at 532 nm with a multi-grating, MgO doped periodically poled stoichiometric lithium tantalate (MgO:sPPLT) as quasi-phase matching (QPM) crystal. By utilizing eight grating periods, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, and 8.8 µm of the QPM crystal, with grating tuning and temperature tuning, the i-SRO can be continuously tuned across 951–793 nm and the corresponding idler tunable over 1212–1620 nm. A maximum signal power of 4.9 W for a pump power of 9.1 W and a relevant pump to signal conversion efficiency of ∼53.8% are achieved at the signal of 821 nm. At a pump power of 5.4 W, the output power stability of the signal at 837 nm is better than 2.1% rms, within one hour in Gaussian spatial beam profile. The SRO performance in tuning rate has also been investigated.

Dissipative localized states and breathers in phase-mismatched singly resonant optical parametric oscillators: Bifurcation structure and stability

We study the emergence of dissipative localized states in phase mismatched singly resonant optical parametric oscillators. These states arise in two different bistable configurations due to the locking of front waves connecting the two coexisting states. In one of these configurations, the bistability is mediated by the coexistence of two uniform states. Here the localized states are organized in a collapsed snaking bifurcation structure. Moreover, these states undergo oscillatory instabilities which lead to a breathing behavior. When the bistability is related to the coexistence of a uniform state and a spatially periodic pattern, localized states are organized in a bifurcation structure similar to the standard homoclinic snaking. Performing an exhaustive bifurcation analysis, we characterize in detail the previous structures, their linear stability, and the modification of their dynamics as a function of the control parameters of the system.

Terahertz radiation in tailored two-color laser fields with a stabilized doubly resonant optical parametric oscillator

Terahertz radiation in tailored two-color laser fields with a stabilized doubly resonant optical parametric oscillator

Experimental Study of Near-Infrared to Mid-Infrared Laser Output Based on Single Resonant Optical Parametric Oscillator

Experimental Study of Near-Infrared to Mid-Infrared Laser Output Based on Single Resonant Optical Parametric Oscillator