Parametric Oscillator Research Articles

Generating tunable picosecond pulses at 900 nm directly from the all-fiber structured parametric oscillator

In this work, we present an all-fiber structured parametric oscillator capable of directly generating pulses within the 900 nm wavelength range. Leveraging the four-wave mixing effect within photonic crystal fibers, the oscillator converts the 1030 nm pump light into two distinct sidebands centered at 900 nm and 1250 nm. Employing time-dispersion-tuning techniques, we achieved a remarkable continuously tunable wavelength range spanning 60 nm, from 865 nm to 925 nm. These pulses exhibited a pulse width of 3.2 ps and a peak power of 500 W at 900 nm, with a repetition rate of 30.6 MHz.

Wavelength-tunable mode-locked fiber laser based on a bending strain-controlled filter

Wavelength-tunable mode-locked fiber lasers are highly versatile and find applications in pump–probe measurement, optical communications, optical parametric oscillation, among others. Herein, we introduce a novel approach for tuning carbon nanotube-based passively mode-locked fiber laser using a bending-based mechanism. Our method involves a bending strain controlled multimode interference all-fiber filter. This filter consists of a hybrid structure built from a cascaded seven-core fiber (SCF)-twin-hole twin-core fiber (THDCF)-SCF. It achieves a continuous wavelength tuning range of 25 nm from 1558 nm to 1583 nm with a tuning efficiency of −3.38 nm/m−1. By increasing the pump power, the dual-wavelength locked modes are also achieved at specific curvature. Owing to advantages of simple structure, low cost, and high bending sensitivity, our tunable filter shows promise for efficient wavelength tuning in ultrafast fiber laser.

High-sensitivity dual-comb and cross-comb spectroscopy across the infrared using a widely tunable and free-running optical parametric oscillator

Dual-comb spectroscopy (DCS) enables high-resolution measurements at high speeds without the trade-off between resolution and update rate inherent to mechanical delay scanning. However, high complexity and limited sensitivity remain significant challenges for DCS systems. We address these via a wavelength-tunable dual-comb optical parametric oscillator (OPO) combined with an up-conversion detection method. The OPO is tunable from 1300-1670 nm (signal) and 2700-5000 nm (idler). Spatial multiplexing in both the laser and OPO cavities creates a near-common path arrangement, enabling comb-line-resolved measurements in free-running operation. The narrow instantaneous bandwidth results in high power per comb-line up to 160 μW in the mid-infrared. Through intra-cavity up-conversion based on cross-comb spectroscopy, we leverage these power levels while overcoming the sensitivity limitations of direct mid-infrared detection. This approach yields a high signal-to-noise ratio (50.2 dB Hz1/2) and high dual-comb figure of merit (3.5 × 108 Hz1/2). This scheme enabled detecting ambient methane over a 3-meter path length in millisecond time scale.

Advancing on-chip Kerr optical parametric oscillation towards coherent applications covering the green gap

Optical parametric oscillation (OPO) in Kerr microresonators can efficiently transfer near-infrared laser light into the visible spectrum. To date, however, chromatic dispersion has mostly limited output wavelengths to >560 nm, and robust access to the whole green light spectrum has not been demonstrated. In fact, wavelengths between 532 nm and 633 nm, commonly referred to as the “green gap”, are especially challenging to produce with conventional laser gain. Hence, there is motivation to extend the Kerr OPO wavelength range and develop reliable device designs. Here, we experimentally show how to robustly access the entire green gap with Kerr OPO in silicon nitride microrings pumped near 780 nm. Our microring geometries are optimized for green-gap emission; in particular, we introduce a dispersion engineering technique, based on partially undercutting the microring, which not only expands wavelength access but also proves robust to variations in resonator dimensions. Using just four devices, we generate >150 wavelengths evenly distributed throughout the green gap, as predicted by our dispersion simulations. Moreover, we establish the usefulness of Kerr OPO to coherent applications by demonstrating continuous frequency tuning (>50 GHz) and narrow optical linewidths (<1 MHz). Our work represents an important step in the quest to bring nonlinear nanophotonics and its advantages to the visible spectrum.

Evaluation of operational parameters for vessel's flexible subsea pipelines

AbstractThe operation of offshore vessels is directly related to the use of flexible pipelines. The article describes in detail the analysis of power, geometric, kinematic and technological parameters that affect the main operational characteristics of these pipes during their operation under water, in rough sea conditions and under wind loads. The article describes the degree of dependence between loads on the pipeline and velocity of the oncoming flow, the geometry of the pipe and the distance to the rigid surface of the ship's hull or the seabed. It was determined how the flow velocity during parametric oscillations of the pipeline in unrestricted flow and near the surface of the seabed affects the change in its drag and lift coefficients. An estimate of operational limits of flexible pipeline instability was obtained. On the base of changes in distributed load, specific values for safe lengths of pipelines were formulated. It has been stated that the probability of failure‐free operation of a flexible pipeline at a level of 0.99 is directly determined by the frequency of its oscillation. Its numerical values should always be at a level that does not exceed 3.7% of the frequency of pipe dynamic oscillations.

A high peak power and low peak-to-peak instability mid-infrared optical parametric oscillator pumped by a 1064 nm electro-optic cavity-dumped pulsed laser

A high peak power and low peak-to-peak instability mid-infrared optical parametric oscillator pumped by a 1064 nm electro-optic cavity-dumped pulsed laser

Enhanced Dye-Sensitized Mechanosensation Utilizing Pulsed and Digitally Modulated Light.

The generation of pressure perturbations in matter stimulated by pulsed light is a method widely recognized as the photoacoustic or light-induced thermoelastic effect. In a series of psychophysical experiments, the robustness of the tactile perception generated with a variety of light sources is examined: a diverging pulsed laser used for photoacoustic tomography optical parameter oscillation (OPO), a miniature diode laser (MDL), and a commercial digital light processing (DLP) projector. It is demonstrated that participants can accurately detect, categorically describe the sensations, and discern the direction of pulsed light travel. High detection accuracy is reported as follows: (d' = 4.95 (OPO); d' = 2.78 (modulated MDL); d' = 2.99 (DLP)) of the stimulus on glabrous skin coated with a thin layer of dye absorber. For all light sources, the predominant sensation is felt as vibration at the distal phalanx (i.e., fingertip, 55.21-57.29%) and the proximal phalanx (41.67-44.79%). At the fingertip, thermal sensations are perceived less frequently than mechanical ones. Moreover, these haptic effects are preserved under a wide range of pulse widths, spot sizes, optical energies, and wavelengths of the light sources. This form of sensory stimulation demonstrates a generalizable non-contact, non-optogenetic, in situ activation of the mechanosensorysystem.

Wave energy converter with multiple degrees of freedom for sustainable repurposing of decommissioned offshore platforms: An experimental study

Targeting at the sustainable repurposing of decommissioned offshore platforms, a novel wave energy converter with a distinct mechanical-motion-rectifier power take-off system is developed to provide renewable energy. A scaled prototype is constructed and experimentally investigated in a large wave tank, as an essential step before sea trials. A new phenomenon of parametric oscillation is observed and explored, as physical evidence of chaotic instabilities of wave energy devices. Several advantages of the multi-degree-of-freedom device over its single-degree-of-freedom counterpart are disclosed physically for the first time. Releasing the pitch and roll degrees of freedom helps enlarge the heave amplitude of the energy-absorbing buoy, receive a larger hydrodynamic force from water waves to the power take-off system, reduce structural deflection and friction of the transmission machinery, and eliminate spiky and noisy vibrations of the internal force. Accordingly, the maximum efficiencies in the energy absorption and transmission stages increase from 45% and 11% to 90% and 30%, respectively; the overall efficiency of energy conversion is increased by up to three times in a broad spectrum of wave conditions.

2.7 μm backward wave optical parametric oscillator source for CO2 spectroscopy.

In this work, a novel 2.7 µm source used for CO2 and H2O vapor spectroscopy using the backward propagating wave of a backward wave optical parametric oscillator (BWOPO) is demonstrated for the first time to our knowledge. The unique properties of BWOPOs eliminate the need for additional spectral narrowing or wavelength stabilization, enabling the use of a multi-longitudinal mode Q-switched pump laser centered around 1030 nm. A full characterization of the source is presented, revealing a central output at 2712 nm, showcasing a temperature tuning of -1.77 GHz/K, and achieving an output pulse energy of 2.3 µJ. Novel methods are introduced for measuring the linewidth and wavelength stability using the ambient laboratory air. These approaches demonstrate a narrow output of 43 pm and establish an upper limit of stability at 65 MHz, with no active means of stabilization. These findings underscore the potential of BWOPOs as a robust platform for future differential absorption lidar (DIAL) systems.

High-power idler-resonant intracavity KTA OPO driven by a dual-loss-modulated Q-switched mode-locked laser with AOM and Sb2Te3 nanosheets

By using Sb2Te3 nanosheets as saturable absorbers (SA) and an acousto-optic modulator (AOM), a laser-diode (LD) end-pumped idler-resonant KTiOAsO4 (KTA)-based intracavity optical parametric oscillator (IOPO) pumped by a dual-loss-modulated Q-switched mode-locked (QML) laser has been realized. The experimental results show that the pulse widths of the Q-switched envelope and the mode-locking pulse numbers underneath the Q-switched envelope decrease as the pump power increases. When the pump power reaches a certain value, only one mode-locking pulse underneath a Q-switched envelope exists, resulting in the generation of the subnanosecond mode-locking pulses of OPO with the repetition rate of AOM. The minimum mode-locking pulse durations of the signal and idler waves were measured to be 545 and 936 ps at an AOM frequency of 1 kHz and a diode pump power of 22.45 W, corresponding to the maximum peak powers of 648 and 185 kW, respectively. Furthermore, a set of coupled rate equations for the dual-loss-modulated QML laser-pumped intracavity idler-resonant OPO was formulated according to the Gauss distribution of intracavity photon density. The numerical simulations of these equations agree with the experimental results. These results collectively suggest the potential application of Sb2Te3 as a promising nanomaterial in the realm of optoelectronics.

Interaction of inertia and magnetic force in the liquid metal flow past a magnetic obstacle

In this paper, we present a numerical study of the three-dimensional behavior of a liquid metal flow in an insulating rectangular duct of narrow cross section past a localized magnetic field (i.e., a magnetic obstacle) produced by two parallel square magnets arranged externally on the walls of the duct. A series of simulations are conducted focused mainly on describing the interplay between inertial and magnetic forces in a wide range of interaction parameters (1.8&amp;lt;N&amp;lt;48) by varying the Reynolds number while the Hartmann number is kept fixed (Ha = 75). The analyzed configuration coincides with that studied experimentally by Domínguez et al. [“Experimental and theoretical study of the dynamics of wakes generated by magnetic obstacles,” Magnetohydrodynamics 51(2), 215–224 (2015)] and, as a first step, experimental data from local variables (streamwise velocity component) and global parameters (oscillation frequency and kinetic energy of the wake) are consistently replicated by the numerical model. Furthermore, to complement the flow phenomenology, the transition to different flow structures as the interaction parameter varies is explored. It is found that when the magnetic forces predominate over inertia, stationary vortex patterns with two, four, and six vortices appear while, unlike the hydrodynamic flow past a bluff body, the increase in inertial effects leads to a reduction in the number of vortices and eventually to their disappearance, reaching a state in which the magnetic obstacle becomes imperceptible to the flow. The existence of a critical value of the interaction parameter that maximizes the kinetic energy of the wake is confirmed numerically and corroborated from the experimental data.

Compact 2-μm Hundred Hertz optical parametric oscillator Based on KTP crystal

A 100 Hz compact 2 μm optical parametric oscillator (OPO) based on a type II non-critically phase-matched KTiOPO4 crystal (KTP) was reported. The monolithic KTP crystal was pumped with a passively Q-switched 1064 nm Nd:YAG laser. At a repetition rate of 100 Hz and a single pulse energy of 5.8 mJ of pump light, a 2128-nm laser output was achieved with a maximum of 1.17 mJ of parametric light at the degenerate point, with a parametric light pulse width of approximately 10.5 ns, corresponding to a pump to parametric light conversion efficiency of 20.1 %.

Finding maximum independent set based on multi-stage simulated quantum adiabatic evolution

The ubiquitous nature of the maximum independent set (MIS) problem across diverse fields, including biology and chip design, presents a significant challenge. Recently, quantum algorithms have been recognized for their increased potential in addressing combinatorial optimization problems, including the MIS problem. Several quantum systems, including optical quantum circuits and Rydberg atomic systems, have been designed specifically for the MIS problem. However, elucidating the precise nature of instances that pose challenges for quantum algorithms constitutes a formidable task. In an effort to comprehend this issue, we endeavor to delineate the conditions under which instances become hard to solve by analyzing the Hamiltonian of the k-independent set (k-IS). Furthermore, we present two multi-stage strategies grounded in the simulated quantum adiabatic evolution (SQAE) of Kerr-nonlinear parametric oscillator (KPO) system for identifying the MIS in instances deemed hard to solve. More specifically, we present the algorithm leveraging SQAE of the KPO system for approximating the MIS. Our investigation of the SQAE algorithm reveals that optimal solutions are unattainable under two distinct conditions: (1) when the number of solutions is exponentially smaller to the problem’s scale, and (2) when the counts of non-optimal independent sets (IS) with m overlaps between the optimal k-IS (k>m) is exponentially smaller relative to the problem’s scale. With these two distinctive features, we propose two multi-stage SQAE strategies tailored for hard-to-solve instances. In the first approach, the SQAE algorithm is executed multiple times to identify a set of candidate vertices for the MIS. For each vertex or combinations of vertices in this set, we extract the subgraphs induced by the vertices not adjacent to them. Subsequently, the SQAE algorithm is applied to the subgraph to obtain the (k−1)-IS. In the second multi-stage strategy, we consider each vertex vi in the given graph, generating the subgraph induced by the vertices not adjacent to vi. The SQAE algorithm is then employed to find the (k−1)-IS of the subgraph. Experimental results demonstrate that both multi-stage strategies significantly enhance the performance of the SQAE algorithm for hard-to-solve instances.

Low-repetition-rate near-infrared femtosecond pulse generation in a harmonically-pumped idler-resonant optical parametric oscillator

Low-repetition-rate near-infrared femtosecond pulse generation in a harmonically-pumped idler-resonant optical parametric oscillator

3- W, 3.8 µm self-optical parametric oscillator by pulsed pumping based on Nd:MgO:PPLN crystal

We present a 3.8 µm self-optical parametric oscillator (SOPO) pumped by a pulsed laser diode (LD) based on only one Nd:MgO:PPLN crystal. The problem of heat accumulation in Nd:MgO:PPLN crystals caused by high-power laser pumping is significantly optimized. The generation of non-matching polarized fundamental light is suppressed, ensuring the output of π-polarized (π-pol) 1084 nm fundamental light across the entire pumping range, and satisfying the polarization matching condition. The mid-infrared SOPO system based on this method is not only compact in structure, and stable in central wavelength, but also improves the self-conversion efficiency. Moreover, a maximum output power of 3.04 W is obtained at 3814 nm in pulse pumping mode, which represents the highest output power in 3.8 µm SOPOs. The corresponding repetition frequency is 25.11 kHz and the single pulse width is 11.45 ns.

Mid-infrared Doppler-free saturation absorption spectroscopy of the Q branch of CH4ν3 = 1 band using a rapid-scanning continuous-wave optical parametric oscillator.

We have developed a mid-infrared Doppler-free saturation absorption spectroscopy apparatus that employs a commercial continuous-wave optical parametric oscillator (CW OPO), complemented by a home-built automation and wavelength scanning system. Here, we report a comprehensive spectral scan of the Q branch transitions of the ν3 = 1 band of methane (CH4) with an average linewidth (FWHM) of 4.5 MHz. The absolute frequency calibration was achieved using previously reported transition frequencies determined using optical frequency combs, while a Fabry-Perot etalon was used for the relative frequency calibration. We report 15 transitions with improved accuracies of 1.13 MHz (3.76 × 10-5 cm-1).

The effects of thermalization on the performance of passively Q-switched IC-OPOs

In this paper, we report a new model for passively Q-switched intracavity optical parametric oscillators (IC-OPOs), using Cr:YAG as a Q-switch crystal. The model considers the effects of thermalization in the Nd:YAG laser crystal, excited state absorption in the Cr:YAG saturable absorber, nonlinear loss due to pump depletion in the nonlinear crystal, the thermal lens effect and the mode overlap of the fields within the nonlinear crystal. The calculated pulse width for the 1,064 nm pump light was 6.2 ns compared to the experimental result of 6 ns, while the signal wave was calculated to have a pulse width of 1.75 ns compared to the experimental result of 2 ns. The model is shown to accurately calculate both the temporal and output power characteristics of the IC-OPO, which has not been previously reported to the best of our knowledge.

Spectral programmable mid-infrared optical parametric oscillator

A spectral programmable, continuous-wave mid-infrared (MIR) optical parametric oscillator (OPO), enabled by a self-developed high-power spectral tailorable fiber laser, was proposed and realized. While operating at a single-wavelength, the maximum idler power reached 5.53 W at 3028 nm, with a corresponding pump-to-idler conversion efficiency of 14.7%. The wavelength number switchable output was available from one to three. The single idler was tunable in a range of 528 nm (2852–3380 nm). In a dual-wavelength operation, the interval between two idlers could be flexibly tuned for 470 nm (53–523 nm), and the intensity of each channel was controllable. Triple-wavelength idler emission was realized, meanwhile exhibiting spectral custom-tailored characteristics. Furthermore, we balanced the parametric gain through the pre-modulating broadband multi-peak pump spectra, enabling a 10 dB bandwidth adjustment of the idler emission from 20 to 125 nm. This versatile mid-infrared laser, simultaneously featuring wide tuning, multi-wavelength operation, and broad bandwidth manipulation, has great application potential in composition detection, terahertz generation, and speckle-free imaging.

Anneal-free ultra-low loss silicon nitride integrated photonics

Heterogeneous and monolithic integration of the versatile low-loss silicon nitride platform with low-temperature materials such as silicon electronics and photonics, III–V compound semiconductors, lithium niobate, organics, and glasses has been inhibited by the need for high-temperature annealing as well as the need for different process flows for thin and thick waveguides. New techniques are needed to maintain the state-of-the-art losses, nonlinear properties, and CMOS-compatible processes while enabling this next generation of 3D silicon nitride integration. We report a significant advance in silicon nitride integrated photonics, demonstrating the lowest losses to date for an anneal-free process at a maximum temperature 250 °C, with the same deuterated silane based fabrication flow, for nitride and oxide, for an order of magnitude range in nitride thickness without requiring stress mitigation or polishing. We report record low anneal-free losses for both nitride core and oxide cladding, enabling 1.77 dB m-1 loss and 14.9 million Q for 80 nm nitride core waveguides, more than half an order magnitude lower loss than previously reported sub 300 °C process. For 800 nm-thick nitride, we achieve as good as 8.66 dB m−1 loss and 4.03 million Q, the highest reported Q for a low temperature processed resonator with equivalent device area, with a median of loss and Q of 13.9 dB m−1 and 2.59 million each respectively. We demonstrate laser stabilization with over 4 orders of magnitude frequency noise reduction using a thin nitride reference cavity, and using a thick nitride micro-resonator we demonstrate OPO, over two octave supercontinuum generation, and four-wave mixing and parametric gain with the lowest reported optical parametric oscillation threshold per unit resonator length. These results represent a significant step towards a uniform ultra-low loss silicon nitride homogeneous and heterogeneous platform for both thin and thick waveguides capable of linear and nonlinear photonic circuits and integration with low-temperature materials and processes.

Infrared spectra of partially deuterated water dimers in the fundamental O-D stretch region.

Spectra of mixed H/D water dimers are studied in the mid-infrared region of the O-D stretch fundamental (2630-2800cm-1) using a pulsed supersonic slit jet and a tunable optical parametric oscillator infrared source. Over 30 bands, belonging to nine of the ten possible isotopologues (only H2O-HOD is missed), are observed and analyzed. The implications for excited state tunneling splittings, lifetime effects, and vibrational shifts are discussed. These are the first significant new experimental results on (gas phase) mixed water dimers in over 25 years, and they are valuable for testing water dimer theoretical calculations, a field which continues to be of lively current interest.