Optical Parametric Oscillator System Research Articles

Multiline molecular tagging velocimetry of nitric oxide at 100 kHz using an injection-seeded burst-mode OPO.

An injection-seeded, burst-mode optical parametric oscillator (OPO) operating at a repetition rate of 100 kHz is used to demonstrate the multiline molecular tagging velocimetry of an underexpanded jet using nitric oxide fluorescence. The very narrow linewidth of the OPO system, along with the relatively high pulse energies of the burst-mode system, enables efficient single-photon excitation of nitric oxide along multiple laser beam lines at a high repetition rate. Simultaneous one-dimensional velocity profile measurements were obtained of an underexpanded jet system at six different locations using a reference initial image and single-shot delayed images. A methodology for calculating the uncertainty of single-shot velocity is also described. Mean and root-mean-square velocity profiles are obtained at multiple locations simultaneously over a sampling time of 1 ms. The high-repetition-rate velocity measurements also appear to capture the onset of velocity oscillations and has the potential to reveal velocity frequency content occurring in the tens of kHz. The demonstrated velocimetry technique could be paired with other emerging burst-mode laser capabilities for a quantitative multiparameter gas property or multicomponent gas velocity measurements for supersonic and hypersonic flows, especially within ground test facilities that are limited to very short run durations.

Spectrally resolved ultrafast transient dynamics of a femtosecond fiber-feedback optical parametric oscillator.

We report on spectrotemporal transient dynamics in a femtosecond fiber-feedback optical parametric oscillator (FFOPO) system. Burst modulation of the pump beam in combination with dispersive Fourier transformation sampling allows to record single-pulse signal spectra at 41 MHz sampling rate. Therefore, each individual pulse of the signal transients can be spectrally resolved. We characterize the signal output behavior for anomalous as well as for normal intra-cavity dispersion. Amongst steady state output we observed period-doubling cycles and other attractors, which occured at higher intra-cavity nonlinearity levels. The experimental findings are supported by numerical simulations, in order to identify the linear and nonlinear effects, which govern the wavelength tuning behavior of this FFOPO system. We find that steady state operation is preferred and that the wavelength tuning stability of the FFOPO dramatically increases when using a normal dispersion feedback fiber.

Luminescent Properties of (Ca7ZrAl6O18-Ca3Al2O6-CaZrO3):Eu3+ Composite Ceramics and Tracing in the Hydration Process

In this work, solid-state reaction sintering was used to fabricate Ca7ZrAl6O18-Ca3Al2O6-CaZrO3:Eu3+ ternary composite ceramics and cements. The structural, microstructural, and spectroscopic properties of the ceramics with different Eu2O3 content were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), and spectrofluorimetry, respectively. The XRD patterns analyzed with Rietveld refinement confirm the presence of the orthorhombic phase of Ca7ZrAl6O18 and the cubic phase of Ca3Al2O6 in all the samples, indicating that doping of Eu3+ slightly changes the crystalline structure of both aluminate phosphors. EDS analysis revealed that the Eu doping element was strongly concentrated to the two phases, i.e., Ca7ZrAl6O18 and Ca3Al2O6, with the Eu concentrations of 8.45 wt.% and 8.26 wt.%, respectively. The luminescent properties of the ceramics doped with different Eu3+ ion concentrations were investigated by excitation and emission spectroscopy at room temperature. These results were compiled using a laser with an optical parametric oscillator (OPO) system. The obtained spectra indicated changes in the luminescence intensity and shape occurring with phase composition and Eu2O3 concentration. The emission spectra of the ceramics exhibit a strong dependence on the excitation wavelength in the range from 210 to 300 nm, and invariably, five peaks were assigned to the 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transitions of Eu3+. The luminescence spectroscopy was then used to trace the early and long-term hydration behavior of cements. Thus, luminescence spectroscopy may provide a new tool for non-destructive testing of cement-based structures.

A versatile and narrow linewidth infrared radiation source for ro-vibration state-selected preparation of molecules in molecular beams.

We describe the design and characterization of a versatile pulsed (5ns, 10Hz repetition rate) optical parametric oscillator and amplifier system capable of generating single longitudinal mode, narrow linewidth (0.01 cm-1) radiations in the wavelength range of 680-870nm and 1380-4650nm. Using a combination of power-normalized photoacoustic signal and a Fizeau interferometer-based wavemeter, we are able to actively stabilize the output wavenumber to within 0.005 cm-1 (3σ) over a timescale longer than 1000s. We demonstrate an application of this system by performing ro-vibration state-selected preparation of CO in the v = 2 state, via direct overtone excitation (v = 0 → 2 at 2346nm) and subsequent state-selected detection in an internally cold molecular beam.

A Stable and Compact Mid-IR at 6.45 μm Exceeding 6 mJ of Pulse Energy BaGa4Se7 Optical Parametric Oscillator

We experimentally demonstrate a stable and compact high pulse energy mid-infrared (MIR) 6.45 μm laser, which is produced by an optical parametric oscillator (OPO) based on the non-oxide BaGa4Se7 (BGSe) nonlinear crystal pumped by 1064 nm Nd:YAG laser oscillator. With optimizing the parameters of the OPO system, a record high idler energy of 6.76 mJ at 6.45 μm was obtained with 18.85 ns of pulse duration (FWHM) at the repetition rate of 10 Hz under 93.5 mJ of pump energy, corresponding to an optical-to-optical conversion efficiency up to 7.23% from 1064 nm to 6.45 μm. The experimental results were in close approximation with the theoretical calculations. To date, it is both the highest MIR pulse energy and the highest conversion efficiency at 6.45 μm for any 1 μm pumped OPOs. Further, excellent output energy stability is demonstrated, with an energy fluctuation of less than ±0.5% over 165 min. Such a laser is interesting for both scientific and medical applications, including, for instance, for trace gas analysis and tissue ablation.

Quantum Nondemolition Measurements with Optical Parametric Amplifiers for Ultrafast Universal Quantum Information Processing

Realization of a room-temperature ultrafast photon-number-resolving quantum nondemolition (QND) measurement would have significant implications for photonic quantum information processing, enabling, for example, deterministic quantum computation in discrete-variable architectures, but the requirement for strong coupling has hampered the development of scalable implementations. In this work, we propose and analyze a nonlinear-optical route to photon-number-resolving QND using quadratic (i.e., χ(2)) nonlinear interactions. We show that the coherent pump field driving a frequency-detuned optical parametric amplifier (OPA) experiences displacements conditioned on the number of signal Bogoliubov excitations. A measurement of the pump displacement thus provides a QND measurement of the signal Bogoliubov excitations, projecting the signal mode to a squeezed photon-number state. We then show how our nonlinear OPA dynamics can be utilized to deterministically generate Gottesman-Kitaev-Preskill states with only additional Gaussian resources, offering an all-optical route for fault-tolerant quantum information processing in continuous-variable systems. Finally, we place these QND schemes into a more traditional context by highlighting analogies between the frequency-detuned optical parametric oscillator and multilevel atom-cavity quantum electrodynamics systems by showing how continuous monitoring of the outcoupled pump quadrature induces conditional localization of the intracavity signal mode onto squeezed photon-number states. Our analysis suggests that our proposal may be viable in near-term χ(2) nonlinear nanophotonics, highlighting the rich potential of the OPA as a universal tool for ultrafast non-Gaussian quantum state engineering and quantum computation.Received 18 October 2022Accepted 8 March 2023DOI:https://doi.org/10.1103/PRXQuantum.4.010333Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasQuantum computationQuantum engineeringQuantum information processingQuantum information processing with continuous variablesQuantum opticsQuantum state engineeringSecond order nonlinear optical processesQuantum InformationAtomic, Molecular & Optical

Holographic recordings without compromise

AbstractWidely tunable continuous‐wave optical parametric oscillator (OPO) systems help meet the demands on holographic optical elements (HOEs) for many use cases, including head‐up displays and augmented reality devices. The wide tuning range allows for direct adjustment of the replay wavelength with little to no need for modification of the holographic recording geometry. HOEs fabricated using these OPO systems in conjunction with advanced photopolymer materials offer precisely controlled replay properties and exceptional diffraction efficiency.

High Pulse Energy, Narrow Linewidth 6.45 μm from an Optical Parametric Oscillator in BaGa4Se7 Crystal

This paper presents a high pulse energy, narrow linewidth, mid-infrared (MIR) laser at 6.45 μm, based on a BaGa4Se7 (BGSe) crystal optical parametric oscillator (OPO) pumped by 1.064 μm laser. The maximum pulse energy at 6.45 μm was up to 1.23 mJ, with a pulse width of 24.3 ns and repetition rate of 10 Hz, corresponding to an optical–optical conversion efficiency of 2.1%, from pump light 1.064 μm to idler light 6.45 μm. The idler light linewidth was about 6.8 nm. Meanwhile, we accurately calculated the OPO phase-matching condition at BGSe crystal pumped by 1.064 μm laser, and a numerical simulation system was performed to analyze the input–output characteristics at 6.45 μm, as well as the effect of crystal length on the conversion efficiency. Good agreement was found between measurement and simulation. To the best of our knowledge, this is the highest pulse energy at 6.45 μm, with the narrowest linewidth for any all-solid-state MIR ns laser in BGSe-OPO pumped by simple 1.064 μm oscillator. This simple and compact 6.45 μm OPO system, with high pulse energy and narrow linewidth, can meet the requirements for tissue cutting and improve tissue ablation accuracy.

Spatial evolution of nitric oxide in ns-discharges using a 250 kHz optical parametric oscillator

In this article we present burst-mode nitric oxide laser-induced fluorescence (LIF) measurements at 250 kHz probing the first 500 µs evolution of a nanosecond repetitively pulsed discharge in the spark regime. The discharge energy was varied from 140 µJ to 180 µJ by adjusting the excitation voltage. The probe laser beam at 226 nm was produced by doubling the 452 nm output of an optical parametric oscillator (OPO) pumped by 355 nm output of a burst-mode laser. It was observed that the nitric oxide produced by the discharge developed a toroidal distribution around the electrode central axis over the first 200 µs after the last spark discharge with the maximum local nitric oxide concentration of 1.8 × 1024 m−3. The expansion of the toroidal distribution was tracked over time and space by the pulse-burst laser pumped OPO system for the first time.

The He-H3 + complex. II. Infrared predissociation spectrum and energy term diagram.

The rotationally resolved infrared (IR) spectrum of the He-H3 + complex has been measured in a cryogenic ion trap experiment at a nominal temperature of 4K. Predissociation of the stored complex has been invoked by excitation of the degenerate ν2 mode of the H3 + sub-unit using a pulsed optical parametric oscillator system. An assignment of the experimental spectrum became possible through one-to-one correlations with bands of the spectrum theoretically predicted in Paper I [Harding et al., J. Chem. Phys. 156, 144307 (2022)]. 19 bands have been assigned and analyzed, and the energy term diagram of the lower states of this floppy molecular complex has been derived from combination differences (CDs) in the experimental spectrum. Ground state combination differences (GSCDs) reveal a large part of the energy term diagram for the He-H3 + complex in its vibrational ground state, v = 0. Experimental and theoretical term energies agree within experimental accuracy for the rotational fine structure associated with the total angular momentum quantum number J and the parity e/f as well as for the coarse spacing of the lowest K states of the complex. This favorable comparison shows that the potential energy surface (PES) calculated in Paper I is accurate. The barriers between the three equivalent global minima in this PES are relatively low and the He-H3 + complex is extremely floppy, with nearly unhindered internal rotation of the H3 + sub-unit. The resulting Coriolis interactions couple the internal and end-over-end rotation of the complex and contribute significantly to the energy terms. They are observed both in experiment and theory and are, e.g., the origin of different rotational constants for states of e and f parity. Also in this respect, experiment and theory agree very well. Despite the assignment and analysis of many bands of the extremely rich IR spectrum of He-H3 +, higher levels of excitation, including the complex stretching mode, need further attention.

High-repetition-rate krypton tagging velocimetry in Mach-6 hypersonic flows.

A 100 kHz krypton (Kr) tagging velocimetry (KTV) technique was demonstrated in a Mach-6 Ludwieg tube using a burst-mode laser-pumped optical parametric oscillator system. The single-beam KTV scheme at 212 nm produced an insufficient signal in this large hypersonic wind tunnel because of its low Kr seeding (≤5%), low static pressure (∼2.5torr), and long working distance (∼1m). To overcome these issues, a new scheme using two excitation beams was developed to enhance KTV performance. A 355 nm laser beam was combined with the 212 nm beam to promote efficient two-photon Kr excitation at 212 nm, and increase the probability of 2 + 1 resonant-enhanced multiphoton ionization by adding a 355 nm beam. A signal enhancement of approximately six times was obtained. Using this two-excitation beam approach, strong long-lasting KTV was successfully demonstrated at a 100 kHz repetition rate in a Mach-6 flow.

Burst-mode femtosecond fiber-feedback optical parametric oscillator

In multiphoton 3D direct laser writing and stimulated Raman scattering applications, rapid and arbitrary pulse modulation with an extremely high contrast ratio would be very beneficial. Here, we demonstrate a femtosecond fiber-feedback optical parametric oscillator (FFOPO) system in combination with pulse picking in the pump beam. This allows tunable signal output at variable burst rates from DC all the way up to 5 MHz. Furthermore, arbitrary pulse sequences can be generated. The rapid signal buildup dynamics provide individual full-power pulses with only two prepulses. This is possible without the requirement for additional injection seeding. Hereby, the intrinsically high intra-cavity losses of the FFOPO system are found to beneficial, as they enable rapid off-switching of the output as signal ring-down is efficiently suppressed. Possible applications are the reduction of the average power while maintaining a high peak power level, as well as tunable arbitrary pulse sequence generation.

A Narrow-Linewidth Optical Parametric Oscillator Inserted with Fabry–Perot Etalon

Nowadays, the Fabry–Perot etalon (F–P) has been widely utilized in the optical parametric oscillator (OPO) to improve the filtering performance. In this paper, we reported an F–P etalon composed of two ultra-thin silicon wafers spaced with the air. The linewidth of the signal laser and the threshold are 0.03 nm and 0.6 W, respectively when the proposed etalon is employed to a OPO system based on the MgO-doped LiNbO3 (MgO: PPLN). A stabilized output at 1492.4 nm is obtained, and a tunable, high-precision filtering performance can be achieved by varying the gap distance of the F–P etalon arbitrarily due to its ultra-thin thickness. In addition, the F–P etalon can work on a very wide bandwidth due to its weak absorption during the infrared and terahertz waveband. The high-precision tuning capability and wide-band function of proposed etalon may benefit many applications, including spectroscopy, filtering, and optical communication.

High-energy nanosecond parametric source at 2.7 µm.

We report a high-energy nanosecond KTiOAsO4-based optical parametric oscillator and amplifier system driven by a 1064-nm, injection-seeded, Q-switched Nd:YAG laser to provide mid-infrared pumping for few-cycle optical parametric chirped-pulse amplification operating in the long-wave infrared spectral regime. An output energy of 10.5 mJ at 2726 nm was obtained from the final power amplifier with a spectral width of 2.8 nm, pulse duration of 1.2 ns, and M2 value of 2.4. The parametric source provides for the second mode of operation, where 10-ns pulses are produced by disabling the electro-optic slicing that enables the 1-ns mode. For 10-ns operation, the source produced energy of 25 mJ with a M2 value of 2.8.

Amelanotic B16-F10 Melanoma Compatible with Advanced Three-Dimensional Imaging Modalities

Amelanotic B16-F10 Melanoma Compatible with Advanced Three-Dimensional Imaging Modalities

100 kHz krypton-based flow tagging velocimetry in a high-speed flow

Krypton (Kr)-based tagging velocimetry is demonstrated in a Kr/N2 jet at 100 kHz repetition rate using a custom-built burst-mode laser and optical parametric oscillator (OPO) system. At this repetition rate, the wavelength-tunable, narrow linewidth laser platform can generate up to 7 mJ/pulse at resonant Kr two-photon-excitation wavelengths. Following a comprehensive study, we have identified the 212.56 nm two-photon-excitation transition as ideal for efficient Kr-based velocimetry, producing a long-lived (∼40µs) fluorescence signal from single-laser-pulse tagging that is readily amenable to velocity tracking without the need for a second "read" laser pulse. This long-lived fluorescence signal is found to emanate from N2-rather than from Kr-following efficient energy transfer. Successful flow velocity tracking is demonstrated at multiple locations in a high-speed Kr/N2 jet flow. The 100 kHz repetition rate provides the ability to perform time-resolved velocimetry measurements in high-speed and even hypersonic flow environments, where standard velocimetry approaches are insufficient to capture the relevant dynamics.

Dual-Wavelength, High-Repetition-Rate, Compact Femtosecond Optical Parametric Oscillator

We demonstrate a dual-wavelength, compact femtosecond optical parametric oscillator (OPO) with high-repetition-rate, which is harmonically pumped by a ~101 MHz Yb-doped fiber laser system. The dual-wavelength output is realized by exploiting the bidirectional off-axis pumping technique, and the multiplication of repetition rate is derived by placing a nonlinear crystal in a miniaturized V-type cavity with only 16.5 cm length. By adjusting the detuning degree of the pump at one end, the maximum dual-wavelength gap is 66 nm from 1497 to 1563 nm. The time interval between the dual wavelengths can be adjusted freely. This is the first report on a dual-wavelength with the high-repetition-rate of GHz-level, femtosecond OPO system.

Enhanced spectral broadening in an optical parametric oscillator based on a PPLN crystal.

We report a chirped-pulse optical parametric oscillator (OPO) generating light pulses with an instantaneous-bandwidth much wider than the parametric gain-bandwidth of nonlinear crystals. Our numerical simulations show that a relatively high residual second-order-dispersion within the OPO cavity is required in order to achieve the maximum signal-bandwidth from an OPO system. Based on this principle, we constructed an OPO using a 3-mm-long PPLN crystal, which produced a signal wave with an instantaneous-bandwidth of 20 THz (at -20 dB) covering 1447-1600 nm, roughly twice as much as the phase-matching bandwidth of the nonlinear crystal. This scheme represents a promising technical route for generating high-repetition-rate, ultrashort optical pulses with a wide bandwidth at various wavelengths, which may benefit many applications, including optical coherence tomography, pulse synthesis and spectroscopy.

Continuous-Wave Widely Tunable MgO:PPLN Optical Parametric Oscillator With Compact Linear Cavity

An efficient continuous-wave, widely tunable, intra-cavity optical parametric oscillator (OPO) based on periodically poled MgO:LiNbO3 (MgO:PPLN) with a compact three-mirror linear cavity was demonstrated. The mode radii of fundamental and OPO cavities with plane and concave mirrors were calculated and theoretically compared. The result shows that the fundamental laser beam could be compressed, and its power density on the MgO:PPLN crystal could be improved by optimizing concave radii of cavity mirrors. Meanwhile, better mode matching between fundamental cavity and OPO cavity could be realized. A widely tunable signal spectrum from 1.43 to $1.79~\mu \text{m}$ and an idler spectrum from 2.62 to $4.16~\mu \text{m}$ were achieved as the OPO system derived by a diode laser end-pumped Nd:YVO4 crystal laser at 1064 nm. The maximum total output power up to 6.35 W (signal output power of about 4.24 W at $1.60~\mu \text{m}$ and idler output power of about 2.11 W at $3.17~\mu \text{m}$ ) and conversion efficiency of 31.6% were obtained at an incident pump power of 20.1 W.

Investigation of OH and CH2O distributions at ultra-high repetition rates by planar laser induced fluorescence imaging in highly turbulent jet flames

For better understanding of the transient behavior of the flow/flame interaction in highly turbulent premixed flames, measurement techniques with sufficient temporal resolution are required. Using a burst-mode laser pumped optical parametric oscillator system, the present work demonstrated an ultra-high-speed diagnostic, for the first time, capable of visualizing hydroxyl radicals (OH) and formaldehyde (CH2O) distributions in a highly turbulent flame at repetition rates up to 140 kHz (i.e. with a temporal resolution of 7.1 μs) to access the Kolmogorov time scales of flames in the distributed/broken reaction zone regime (Ka ≥ 100). More than 100 consecutive images were recorded in the present work for OH planar laser induced fluorescence (PLIF) measurement at 100 kHz. Systematic temporal and spatial evolution of the flame structure is clearly resolved over long sequences, e.g. 1.2 ms for OH PLIF and 10 ms for CH2O PLIF respectively. The Kolmogorov time scale for all the cases at x/d = 10 and x/d = 30 are estimated with the minimum Kolmogorov time scale of 7.5 μs, indicating that nearly all time-scales of the flow are resolved with the present experimental setup. The axial velocity of the CH2O structure at its outer layer at different flame height positions, UCH2O, is obtained. The velocity UCH2O is compared with the LDV results, which shows a good agreement with the mean flow velocity. By comparing UCH2O with the local axial velocity, different mechanisms responsible for the large-scale wrinkle structures in the reaction zone and the propagation of CH2O structure along the flame height are discussed. Power spectral density and autocorrelation function based on the CH2O outer layer fluctuation in the radial direction are illustrated. Quantitative analysis of the ultra-high-speed diagnostics data further augments the understanding of turbulent combustion down to Kolmogorov scale experimentally.