Continuous-wave singly resonant optical parametric oscillator pumped by a single-frequency resonantly doubled Nd:YAG laser

Threshold and Laser Conversion in Nanostructured-Resonator Parametric Oscillators

We explore optical parametric oscillation (OPO) in nanophotonic resonators, enabling arbitrary, nonlinear phase matching and nearly lossless control of energy conversion. Such pristine OPO laser converters are determined by nonlinear light-matter interactions, making them both technologically flexible and broadly reconfigurable. We utilize a nanostructured inner-wall modulation in the resonator to achieve universal phase matching for OPO-laser conversion, but coherent backscattering also induces a counterpropagating pump laser. This depletes the intraresonator optical power in either direction, increasing the OPO threshold power and limiting laser-conversion efficiency, the ratio of optical power in target signal and idler frequencies to the pump. We develop an analytical model of this system that emphasizes an understanding of optimal laser-conversion and threshold behaviors, and we use the model to guide experiments with nanostructured-resonator OPO laser-conversion circuits, fully integrated on chip and unlimited by group-velocity dispersion. Our Letter demonstrates the fundamental connection between OPO laser-conversion efficiency and the resonator coupling rate, subject to the relative phase and power of counterpropagating pump fields. We achieve (40±4)  mW of on-chip power, corresponding to (41±4)% conversion efficiency, and discover a path toward near-unity OPO laser-conversion efficiency.

Power Scaling of CW Crystalline OPOs and Raman Lasers

Optical parametric oscillators (OPOs) and Raman lasers are two nonlinear-based laser technologies that extend the spectral range of conventional inversion lasers. Power and brightness scaling of lasers are significant for many applications in industry, medicine, and defense. Considerable advances have been made to enhance the power and brightness of inversion lasers. However, research around the power scaling of nonlinear lasers is lacking. This paper reviews the development and progress of output power of continuous-wave (CW) crystalline OPOs and Raman lasers. We further evaluate the power scalability of these two laser technologies by analyzing the cavity architectures and gain materials used in these lasers. This paper also discusses why diamond Raman lasers (DRLs) show tremendous potential as a single laser source for generating exceedingly high output powers and high brightness.

Efficient scheme for mid-infrared generation using simultaneous optical parametric oscillators and DFG processes in a double-pass pump configuration

We present numerical results of an efficient scheme for mid-infrared generation using simultaneous quasi-phase matched optical parametric oscillators (OPO) and difference-frequency generation (DFG) processes in a singly resonant cavity with double-pass pump configuration. Considering an appropriately poled grating structure in MgO doped congruent lithium niobate, we have shown that it is possible to realize the double-pass pump singly resonant (DPSR) cavity configuration for the simultaneous OPO+DFG process, unlike the cascaded interaction scheme, leading to efficient mid-IR generation. Our numerical results are in agreement with the recently reported experimental results. We also present optimum parameters for the DPSR cavity configuration that could provide maximum conversion efficiency.

Antiresonant ring output-coupled continuous-wave optical parametric oscillator

We demonstrate the successful deployment of an antiresonant ring (ARR) interferometer for the attainment of optimum output coupling in a continuous-wave (cw) optical parametric oscillator (OPO). The cw OPO, configured as a singly-resonant oscillator (SRO), is based on a 50-mm-long MgO:PPLN crystal and pumped by cw Ytterbium-fiber laser at 1064 nm, with the ARR interferometer integrated into one arm of the standing-wave cavity. By fine adjustment of the ARR transmission, a continuously variable signal output coupling from 0.8% to 7.3% has been achieved, providing optimum output coupling for signal and optimum power extraction for the idler, at different input pumping levels. The experimental results are compared with theoretical calculations for conventional output-coupled cw SRO, and the study shows that by reducing the insertion loss of the ARR elements, the performance of the ARR-coupled cw SRO can be further enhanced. We also show that the use of the ARR does not lead to any degradation in the cw SRO output beam quality. The proof-of-principle demonstration confirms the effectiveness of the technique for continuous, in situ, and fine control of output coupling in cw OPOs to achieve maximum output power at any arbitrary pumping level above threshold.

Continuous wave monolithic quasi-phase-matched optical parametric oscillator in periodically poled lithium niobate

We demonstrate a monolithic and quasi-phasematched singly resonant cw optical parametric oscillator in periodically poled lithium niobate. The threshold is 1.0 W and the OPO delivers up to 0.98 W signal power tunable between 1750 and 1950 nm (2710 and 2340 nm idler, respectively). We identify cascaded parasitic oscillation effects and analyze their behavior theoretically, showing good agreement with our experiment. The analysis of parasitic effects points the way to improved device designs that should enable stable, compact, and frequency-tunable sources.

A continuous-wave optical parametric oscillator around 5-μm wavelength for high-resolution spectroscopy

We present a continuous-wave optical parametric oscillator (OPO) capable of high resolution spectroscopy at wavelengths between 4.8 μm and 5.4 μm. It is based on periodically poled lithium niobate (PPLN) and is singly resonant for the signal radiation around 1.35 μm. Because of the strong absorption of PPLN at wavelengths longer than 4.5 μm, the OPO threshold rises to the scale of several watts, while it produces idler powers of more than 1 mW and offers continuous tuning over 15 GHz. A supersonic jet spectrometer is used in combination with the OPO to perform measurements of the transient linear molecule Si(2)C(3) at 1968.2 cm(-1). Fifty rovibrational transition frequencies of the ν(3) antisymmetric stretching mode have been determined with an accuracy on the order of 10(-4) cm(-1), and molecular parameters for the ground and the v(3) = 1 state have been determined most precisely.

One-Watt level mid-IR output, singly resonant, continuous-wave optical parametric oscillator pumped by a monolithic diode laser

We report more than 1.1 Watt of idler power at 3373 nm in a singly resonant optical parametric oscillator (SRO), directly pumped by a single-frequency monolithic tapered diode laser. The SRO is based on a periodically poled MgO:LiNbO3 crystal in a four mirror cavity and is excited by 8.05 W of 1062 nm radiation. The SRO pump power at threshold is 4 W. The internal slope-efficiency and conversion efficiency reach 89% and 44% respectively. The signal and idler waves are temperature tuned in the range of 1541 to 1600 nm and 3154 to 3415 nm respectively. To the best of our knowledge, this is the highest output obtained for a diode pumped optical parametric oscillator (OPO), and the first time a SRO is directly pumped by a monolithic tapered diode laser.

Continuous-wave singly-resonant optical parametric oscillator with resonant wave coupling

We report major enhancements in the overall performance of continuous-wave singly-resonant optical parametric oscillators (cw SROs) through finite output coupling of the resonant wave. Using a cw SRO based on MgO:sPPLT pumped at 532 nm, we demonstrate improvements of 1.08 W in total output power, 10% in total extraction efficiency, and a 130-nm extension in the useful tuning range, while maintaining pump depletions of 70%, idler output powers of 2.59 W, and a minimal increase in oscillation threshold of 24%. The output-coupled cw SRO can deliver a total power of up to 3.6 W at 40% extraction efficiency across 848-1427 nm. The single-frequency resonant wave also exhibits a higher spectral purity than the non-resonant output.

Spectral broadening and stimulated Raman conversion in a continuous-wave optical parametric oscillator

We have confirmed that single-frequency oscillation of a continuous-wave singly resonant optical parametric oscillator is limited to operation below a critical value of the pumping ratio, as predicted by early theoretical treatments. We also report different regimes of spectral broadening as well as stimulated Raman conversion of the signal wave above this critical pump level. We show that spectral broadening may be eliminated by implementing output coupling of the signal wave and demonstrate 8.6 W of total signal and idler output with single-frequency spectra at both wavelengths for 14.5 W of pump power.

High spectral purity and tunable operation of a continuous singly resonant optical parametric oscillator emitting in the red

Continuous-wave oscillation of a singly resonant optical parametric oscillator operating from 619 to 640 nm has been obtained. Parametric gain is created in a MgO-doped periodically poled stoichiometric lithium tantalate crystal pumped at 532 nm. 100 mW of single-frequency red light have been generated. The signal frequency is tunable, and its frequency stabilization on an external reference has been achieved.

Single-frequency quasi-continuous red radiation generated by a green-pumped singly resonant optical parametric oscillator

We demonstrate the operation of a quasi-continuous-wave optical parametric oscillator (OPO) in the red part of the visible spectrum by direct pumping from a frequency-doubled quasi-continuous-wave Nd:YAG laser. The OPO is singly resonant and based on a MgO-doped periodically poled stoichiometric lithium tantalate crystal. A single-frequency 1.2 W output power is obtained when an etalon is inserted inside the cavity.

Efficient generation of coherent blue light at 440 nm by intracavity-frequency-tripling 1319-nm emission from a Nd:YAG laser

A new route for efficiently generating coherent blue light has been explored based on intracavity effective third-harmonic generation in one partly periodically poled KTiOPO4 crystal placed inside the cavity of a diode-pumped Nd:YAG laser. To achieve efficient conversion, we use a dual-temperature oven to separately control the phase-matching conditions for the two second-order nonlinear processes. In addition, a Fabry-Perot cavity at 660 nm is incorporated into the crystal to increase the blue power significantly. When the laser is Q switched to produce long pulses, an average power of 118 mW is generated at 440 nm at a pump power of 10 W.

Continuous-wave singly resonant optical parametric oscillator placed inside a ring laser

A cw singly resonant optical parametric oscillator (SRO) was built and placed inside the cavity of a ring laser. The system consists of a diode-end-pumped Nd:YVO4 ring laser with intracavity periodically poled lithium niobate as the nonlinear gain medium of the SRO. When the laser was operated in a unidirectional mode, we obtained more than 520 mW of signal power in one beam. When the laser was operated in a bidirectional mode, we obtained 600 mW of signal power (300 mW in two separate beams). The power and the spectral features of the laser in the unidirectional and bidirectional modes were measured while the laser was coupled with the SRO. The results show that it is preferable to couple a SRO with a unidirectional ring laser.

Tunable continuous-wave doubly resonant optical parametric oscillator by use of a semimonolithic KTP crystal

A temperature-tuned continuous-wave doubly resonant optical parametric oscillator (OPO) consisting of a semimonolithic KTP crystal and a concave mirror has been designed and built. Under single-axial-mode-pair operation, we obtained a combined output power of the signal and idler light fields up to 365 mW at a pump power of 680 mW. The output wavelength of the OPO can be temperature tuned by as much as 9 nm. We achieved 2.8-GHz continuous frequency tuning of the OPO by tuning the pump laser frequency.

Electro-optic detection of continuous-wave mid-infrared radiation

We demonstrate coherent detection of continuous-wave mid-infrared radiation. This radiation is produced by use of conventional difference-frequency mixing and detected via the linear electro-optic effect. The detection process allows for the simultaneous measurement of the amplitude and phase properties of the infrared field. Both processes require an amplitude-modulated optical beam that is derived from the superimposed output of two single-frequency lasers. With appropriate choice of lasers and nonlinear optical crystals, the technique may be applied to any wavelength throughout the far and mid infrared.

Wide-bandwidth 25-dB amplitude noise suppression in a pump-and-signal-resonant optical parametric oscillator

We present a pump-and-signal-resonant optical parametric oscillator that provides 25 dB of amplitude noise suppression of the transmitted pump beam from dc to 20 kHz. The upper frequency range of the optical limiter increases as the pump power is increased, up to 1 MHz with 580 mW of input power. The amount of noise suppression is limited by pump-depletion effects. The upper frequency range is limited by the temporal response of the device. We present a numerical analysis that predicts this behavior.

Diode-pumped singly resonant continuous-wave optical parametric oscillator with wide continuous tuning of the near-infrared idler wave

We demonstrate wide, continuous tuning of the single-frequency idler wave of a cw singly resonant optical parametric oscillator (SRO). The SRO consists of a periodically poled LiNbO(3) crystal for quasi-phase matching in a four-mirror signal-resonant ring cavity. The SRO, excited by 2.25 W of 924-nm radiation from an InGaAs diode laser, generates as much as 200 mW of single-frequency 2.1-mum idler radiation. We tune the idler frequency continuously within a range as large as 56 GHz by changing the wavelength of the diode pump laser. The versatility of this continuously tunable single-frequency infrared source is demonstrated by recording of N(2)O rovibrational absorption lines near 2.1 mum.

Parametric Generation of Tunable Light from Continuous-Wave to Femtosecond Pulses

By exploiting nonlinear optical effects, a technology of unprecedented flexibility for the production of tunable coherent light has been developed. Referred to as optical parametric generation, it provides sources with spectral coverage extending all the way from the ultraviolet to the mid-infrared, and with temporal coverage extending over all time domains from the femtosecond pulse to the continuous wave. Such sources generate coherent light of outstanding optical quality and are now finding wide-ranging applications.

Singly resonant continuous-wave optical parametric oscillator pumped by a diode laser

We report on what is believed to be the first singly resonant cw optical parametric oscillator (SRO) that is directly pumped by a diode laser. The SRO consists of a 38-mm-long periodically poled LiNbO(3) crystal in a four-mirror signal-resonant ring cavity. Pumped by 2.5 W of 925-nm diode-laser radiation, the SRO generates 480 mW of single-frequency idler radiation at 2.1mum . The wavelengths of the signal and the idler output are tuned in the ranges of 1.55 to 1.70mum and 2.03 to 2.29mum, respectively, by tuning the wavelength of the diode laser from 924.0 to 925.4 nm.

Continuous-wave optical parametric oscillator based on periodically poled KTiOPO(4)

We report what is to our knowledge the first demonstration of a continuous-wave optical parametric oscillator (OPO) based on periodically poled KTiOPO(4) . The 10-mm-long flux-grown crystal had a quasi-phase-matched period of 9mum . The pump source was a miniature frequency-doubled Nd:YAG laser, and the threshold power of this doubly resonant device was 51 mW. The OPO was operated near room temperature. The signal and the idler wavelengths could be tuned in the range 1037-1093 nm by variation of the crystal temperature (32-38 degrees C) and the cavity length. Unlike in other nonlinear crystals, green-induced infrared absorption was not observed up to the highest pumping intensity of approximately 4.5kW/cm(2) .

Generation and application of twin beams from an optical parametric oscillator including an alpha-cut KTP crystal

Measurement slight amounts of absorption of light with accuracy beyond the standard quantum limit has been experimentally demonstrated. The quantum-correlated twin beams used in the measurement were generated from a nondegenerate optical parametric oscillator including an alpha-cut KTiOPO(4) crystal pumped by an intracavity frequency-doubled Nd:YAG laser. The noise in the intensity difference between the twin beams was reduced by 88% below the standard quantum limit (SQL). The signal-to-noise ratio was improved by 7 dB with respect to the SQL of the total light employed in the experiment and by 4 dB with respect to that of the signal light.

Continuous-wave 532-nm-pumped singly resonant optical parametric oscillator based on periodically poled lithium niobate

We report a continuous-wave (cw) 532-nm-pumped singly resonant optical parametric oscillator (SRO) based on periodically poled lithium niobate. The pump source is a commercial 5-W cw diode-pumped, multilongitudinal-mode, intracavity-doubled Nd:YVO(4) laser. Using a four-mirror ring SRO cavity and single-pass pumping, we achieved subwatt internal oscillation threshold, 56% quantum efficiency, and output tuning from 917 to 1266 nm.

Application of a continuously tunable, cw optical parametric oscillator for high-resolution spectroscopy

We report the use of a smoothly tunable, single-frequency continuous-wave optical parametric oscillator (OPO) for high-resolution spectroscopy. The OPO is based on potassium titanyl phosphate and is resonant for both signal and idler fields, resulting in a device with a very low pump power threshold of 30 mW. The frequency-selective nature of the doubly resonant oscillator ensures that the signal and idler modes can be tuned across the entire phase-match bandwidth without the need for additional intracavity frequency-selective components. Smooth frequency tuning of the output of the OPO is obtained by tuning of the pump laser. To demonstrate the practicality of our OPO we recorded the absorption spectrum of cesium vapor in the 1-microm spectral region.

1.1-W single-frequency 532-nm radiation by second-harmonic generation of a miniature Nd:YAG ring laser

A compact and efficient source of cw single-frequency radiation at 532 nm with excellent long-term stability has been realized by external frequency doubling of a diode-pumped miniature Nd:YAG ring laser. With a semimonolithic MgO:LiNbO(3) resonator an optical-to-optical conversion efficiency of 89% from 1064 to 532 nm at an output power of 1.1 W was achieved, with a wall plug efficiency of 9%. This system represents an ideal pump source for narrow-linewidth cw optical parametric oscillators with good frequency stability.

Continuous-wave singly resonant optical parametric oscillator based on periodically poled LiNbO(3)

We report a continuous-wave singly resonant optical parametric oscillator (OPO) based on periodically poled lithium niobate. The simple, two-mirror OPO, pumped by a 1.064-microm Nd:YAG laser, had a 2.6-4.5-W threshold and an output of >1.2 W at 3.3 microm and was tuned over 1.45-1.62 microm (signal) and 3.98-3.11 microm (idler). The noise characteristics and the spectral properties of the device are described.

Continuous-wave singly resonant pump-enhanced type II LiB(3)O(5) optical parametric oscillator

We report what is to our knowledge the first demonstration of a pump-enhanced singly resonant continuous-wave optical parametric oscillator. The nonlinear material used was lithium triborate cut for noncritical phase matching along the z axis, and the device was pumped by a single-frequency argon-ion laser. The oscillation threshold was ~1.0 W at 514.5 nm. For 3.4 W of pump power, we obtained single-frequency output powers of 500 mW in the nonresonant wave, which we temperature tuned over 14 nm.

Continuous-wave total-internal-reflection optical parametric oscillator pumped at 1064 nm

We report what is to our knowledge the first cw 1064-nm-pumped optical parametric oscillator (OPO), using a critically phase-matched (theta(pm) = 45.5 degrees ), monolithic total-internal-reflection, doubly resonant OPO fabricated from congruent LiNbO(3). Frustrated total-internal-reflection provides variable output coupling for the signal and the idler. The measured finesse of 6000 at 2014 nm implies a round-trip power loss of 0.1%. The low round-trip power losses compensate the 2 degrees Poynting vector walk-off and give a threshold of 130 mW. A passive thermal feedback mechanism causes the OPO to oscillate stably in a single axial-mode pair for more than 30 min. The OPO output tunes in 0.1-nm steps from 2040 to 2225 nm by tuning the pump frequency.

1.9-W cw ring-cavity KTP singly resonant optical parametric oscillator

We report high-power and single-frequency operation of a continuous-wave singly resonant potassium titanyl phosphate (KTiOPO(4)) optical parametric oscillator in a ring-cavity configuration. The ring singly resonant optical parametric oscillator threshold is 4.3 W. When the oscillator is pumped by 6.7 W of 532-nm radiation from an 11.2-W single-frequency resonantly doubled Nd:YAG laser, 1.9 W of single-axial-mode output is generated at the idler wavelength of 1039 nm.