Idler Conversion Efficiency Research Articles

Toward generation of mid-infrared orbital angular momentum beams by tailoring four-wave mixing in chalcogenide photonic crystal fiber

The nonlinear process of orbital angular momentum (OAM) beams in multimode fiber has attracted renewed interest due to its enhanced intermodal nonlinear interactions. Here, we designed and simulated a novel photonic crystal fiber (PCF) based on A s 2 S e 3 glass that supports stable OAM modes. By optimizing the structure parameters of the fiber, both the effective index separation and the phase-matching condition of OAM modes were satisfied in the fiber. Mid-infrared OAM light can be generated by intermodal four-wave mixing in the chalcogenide fiber. The idler conversion efficiency at the 5 µm waveband and the signal optical gain spectrum near 1.9 µm is calculated when the pump light is around 2.8 µm. Furthermore, the crosstalk of the FWM process from the other vector modes vanished due to the lower overlap factor compared with the interacting OAM modes. Our work demonstrates that the vortex beam at 5 µm could be generated, and its conversion efficiency can reach 21.96% with appropriate optimization.

Optical parametric gain in CMOS-compatible sub-100 μm photonic crystal waveguides

Emerging compositionally engineered complementary metal-oxide-semiconductor (CMOS)-compatible platforms have been employed for high efficiencies in various on-chip applications, including optical parametric amplification and wavelength conversion. Combining the novel nonlinear optics platforms such as ultra-silicon-rich nitride (USRN: Si7N3) with periodic waveguide structures can lead to further enhancement of material nonlinearities via the slow light effect and enable ultra-compact devices. Four-wave mixing in a USRN-based, CMOS-compatible, photonic crystal waveguide (PhCWg) leading to on/off optical parametric signal gain reaching 3 dB, and a large instantaneous idler conversion efficiency of −1 dB is explored experimentally. Enhancement of Kerr nonlinearity in the presence of a sizable and near-constant group index allows the findings on an ultra-compact, 97 μm-long PhCWg, equivalent to a large on/off gain per unit length of 333 dB/cm.

Influence of linear coupling and group delay fluctuations on intermodal four wave mixing in few mode fiber

We present numerical and experimental study on the origin of fluctuations in the idler power in partially degenerate intermodal four wave mixing in a 1 km long few mode graded index fiber where both the fundamental and higher order modes are excited in both pump and signal wavelengths. Numerical simulation is carried out in the presence of different types of mode coupling processes and group delay fluctuations in order to independently predict the influence of these phenomena by considering the appropriate statistics of the corresponding processes. We propose a quasi-distributed model by choosing the locations of specific coupling events statistically, in correspondence to their correlation lengths. Idler conversion efficiency is experimentally evaluated for different detuning frequencies between the signal and pump through multiple trials, and it is found that even though distinct features of maxima and minima are retained, there are fluctuations in frequencies corresponding to maxima and minima. These experimental results are compared with those from numerical simulations in order to identify the origin of fluctuations.

Numerical study on mid-infrared optical parametric amplification around 5 µm by injecting signal vector beams in As2Se3 MOFs

The influence of the core diameter and pump wavelength on the phase-matching conditions when different signal vector beams are injected is analyzed numerically in a suspended-core ${{\rm As}_2}{{\rm Se}_3}$As2Se3 microstructured optical fiber (MOF). The idler wavelengths satisfying the phase-matching conditions with different signal vector beams can reach wavelengths of 4.8–5.9 µm in the ${{\rm As}_2}{{\rm Se}_3}$As2Se3 MOFs with different core diameters. By changing the signal vector mode field and adjusting the corresponding signal wavelength, the idler wavelength can be tuned in 754.8 nm from 4.9182 to 5.6730 µm with the pump wavelength changing from 2.80 to 2.90 µm. The influence on signal gain and the idler conversion efficiency is calculated in the ${{\rm As}_2}{{\rm Se}_3}$As2Se3 MOFs with different lengths when injecting different signal vector beams. The peak gain of signal and idler conversion efficiency can reach $\sim{28}\,\, {\rm dB}$∼28dB and $\sim{24}\% $∼24%, respectively, when the different signal vector beams are injected. The simulated results demonstrate that the optical parametric oscillation with wavelengths longer than 5 µm can be realized in chalcogenide fibers with signal vector beam injection.

A multi-layer platform for low-loss nonlinear silicon photonics

We demonstrate four-wave mixing (FWM) interactions in a-Si:H waveguides in a multilayer integrated silicon photonic chip. The a-Si:H waveguides are accessed through interlayer couplers from waveguides composed of SiNx. The interlayer couplers achieve a coupling of 0.51 dB loss per transition at the target wavelength of 1550 nm. We observe greater idler power extraction and conversion efficiency from the FWM interaction in the interlayer-coupled multilayer waveguides than in single-material waveguides.

Investigation on four-wave mixing toward mid-infrared waveband in tellurite photonic crystal fiber

The evolution characteristics of the degenerate four-wave mixing (DFWM) effect in the proposed tellurite photonic crystal fiber (PCF) are investigated systematically. The influence of the pitch distance and diameter-to-pitch ratio on the phase-matching condition is analyzed numerically. The effects of fiber length, signal wavelength, idler wavelength, initial pump power and initial signal power on the signal gain and idler conversion efficiency are investigated. Based on the DFWM occurring in the proposed tellurite PCF, the signal (anti-Stokes) wave is efficiently amplified and the idler (Stokes) wave is efficiently generated at the mid-infrared (mid-IR) waveband with the pump wavelength of 1.553 μm. The signal gain can be increased by increasing the initial pump power. The idler conversion efficiency can reach ~ 26%. The simulated results will be instructive for the experimental FWM process to generate mid-IR optical parametric oscillators.

Improved conversion efficiency and beam quality of miniaturized mid-infrared idler-resonant MgO:PPLN optical parametric oscillator pumped by all-fiber laser

We present a miniaturized idler-resonant all-fiber-laser-pumped optical parametric oscillator (OPO) based on MgO:PPLN. The conversion-efficiency and beam-quality performances of the idler- and signal-resonant OPOs with flat-flat cavity are first compared. The idler-resonant OPO MIR beam quality is better than that of the signal-resonant one, but the idler conversion efficiency is lower. Next, we examine the influence of the output-coupler curvature radius, pump-beam-waist radius, and cavity length on the MIR conversion efficiency and beam quality of the idler-resonant OPO. Post optimization of these factors, we report a maximum MIR power of 5.84 W at 3.76 µm, conversion efficiency >14.0%, and M2 factors of 1.57 and 1.49 along the horizontal and vertical directions, respectively.

Broadband incoherent four-wave mixing and 27 dB idler conversion efficiency using ultra-silicon rich nitride devices

The generation of broadband light within the telecommunication band has been instrumental to the design and characterization of advanced optical devices and systems. In this paper, stimulated degenerate four-wave mixing of an ultra-silicon rich nitride waveguide is investigated using a pulsed pump at 1.555 μm and incoherent broadband sources emitting in the 1.65 μm wavelength region as a signal. The waveguide possesses a large nonlinear parameter of 330 W−1/m as well as anomalous dispersion, required for phase matched parametric processes. The broadband idler ranging from 1.43 μm to 1.52 μm is generated using a coupled peak power of 4.6 W, spanning ∼100 nm at the −20 dB level, which is sufficient to cover parts of the E- and S-bands. The spectral span of the generated idler also agrees well with the calculation based on the phase-matching condition governing degenerate four-wave mixing. Cascaded incoherent four-wave mixing is also observed. Using a supercontinuum pump spanning from 1.1 to 1.7 μm with a coupled peak power of 26 W, an idler spanning from 1.2 to 1.4 μm is generated, equivalent to an idler on/off conversion efficiency of 27 dB.

Mid-infrared continuous-wave parametric amplification in chalcogenide microstructured fibers

The persistent growth of interest in the middle infrared (MIR) is stimulating the development of sources and components. Novel waveguides and fibers for the efficient use of nonlinear effects in the MIR are being intensively studied. Highly nonlinear silica fibers have enabled record performances of highly versatile parametric processes in the telecommunication band. However, no waveguiding platforms (to our knowledge) have yet solved the trade-off among high nonlinearity, low propagation losses and dispersion in the MIR. As single waveguide designs have not yet hit this particular optimal point, only pulsed–pumped demonstrations have been carried out, hindering any application requiring narrow linewidth, continuous-wave (c.w.) operation, or signal modulation. Here, we show MIR c.w. parametric amplification in a Ge10As22Se68 tapered fiber. Leveraging state-of-the-art fabrication techniques, we use a photonic crystal fiber (PCF) geometry combining high nonlinearity and low dispersion, while maintaining single mode and low losses in the short-wave IR and MIR. We experimentally demonstrate 5 dB signal amplification and 3 dB idler conversion efficiency using only 125 mW of pump in the 2 μm wavelength range. Our result is not only the first c.w. parametric amplification measured at 2 μm in any waveguide, but it also establishes GeAsSe PCF tapers as the most promising all-fibered, high-efficiency parametric converter for advanced applications in the MIR.

Highly efficient picosecond degenerate four-wave mixing in a tellurite microstructured optical fiber

Wavelength-tunable picosecond degenerate four-wave mixing was demonstrated in a tellurite microstructured optical fiber (TMOF). The zero-dispersion wavelength of the TMOF was shifted to 1570 nm by introducing a single ring of air holes in the cladding. The anti-Stokes signal sideband can be generated from 1490 to 1500 nm, and the Stokes idler sideband can emit from 1595 to 1645 nm. Because of the high nonlinearity of the TMOF and the large peak power of the picosecond pump, a maximal signal gain of 31.2 dB and an idler conversion efficiency of +35 dB were achieved.

Flexible wavelength conversion based on four‐wave mixing in tellurite microstructured optical fibre

On the basis of the tuned four-wave mixing generated in a tellurite microstructured optical fibre, flexible and efficient wavelength conversion can be realised. The signal at 1494 nm can be converted to any wavelength in the band from 1598 to 1641.5 nm by tuning the pump wavelength. A 27.6 dB maximum idler conversion efficiency has been achieved.

Subnanosecond, mid-IR, 05 kHz periodically poled stoichiometric LiTaO_3 optical parametric oscillator with over 1 W average power

We report a subnanosecond mid-IR tunable optical parametric oscillator based on periodically poled stoichiometric lithium tantalate (PPSLT), pumped by an amplified single frequency microchip laser at 1064 nm at a repetition rate of 0.5 kHz. Using a 20 mm long PPSLT crystal polled with three different domain periods (30.2, 30.3, and 30.4 μm) and changing the temperature of the crystal from 20°C to 265°C, we achieved wavelength tuning between 2990 and 3500 nm. The high nonlinearity of the used medium and the large aperture (3.2 mm) ensure maximum idler output energy of ~2 mJ in the whole tuning range, corresponding to 18% idler conversion efficiency and more than 1 W of average power. 270 ps idler pulse durations were obtained as a result of the 818 ps pulse duration of the pump.

High-energy kHz mid-IR tunable PPSLT-based OPO pumped at 1064 nm

We report a single-frequency sub-nanosecond optical parametric oscillator (OPO) based on periodically poled stoichiometric lithium tantalate (PPSLT), pumped by a 1064-nm amplified microchip laser at a repetition rate of 0.5 kHz. Using a 11-mm-long PPSLT crystal polled with three different domain periods (30.2, 30.3, 30.4 μm) and changing the temperature of the crystal from 20 °C to 265 °C, we have achieved wavelength tuning between 2990 nm and 3500 nm. The high nonlinearity of the used medium and the large aperture (2 mm) ensure the maximum idler output energy of ∼0.5 mJ in the whole tuning range, corresponding to average ∼10.5 % idler conversion efficiency and ∼250 mW of average power. Sub-nanosecond pulse durations have been obtained for the idler at 0.88-ns pulse duration of the pump.

Multiple-wavelength quasi-phase-matching for efficient idler generation in MgO:LiNbO3 based nanosecond optical parametric oscillator

We present numerical results for optimization of the overall idler conversion efficiency of a nanosecond optical parametric oscillator (OPO), wherein the signal generated in the OPO process is also used as the pump for a difference frequency generation (DFG) process in a quasi-periodic MgO:LiNbO(3) crystal. The phase-matching conditions are considered such that the generated idler frequencies in both the processes (i.e., OPO and DFG) coincide. Optimization for the idler generation has been performed with respect to the different parameters, such as input pump power, pump pulse duration, and the output coupler reflectivity, for quasi-phase-matched interaction in MgO:LiNbO(3). Wavelength of the pump, signal, and idler waves considered in the optimization are 1.064 μm, 1.456 μm, and 3.95 μm, respectively. A maximum overall idler generation efficiency of ≈33% could be obtained in the simultaneous OPO+DFG process for a pump pulse duration of 72 ns and output coupler reflectivity (R(s)) of 90%, whereas for the stand-alone OPO process, the maximum idler generation efficiency was found to be ≈15%. The optimization has been illustrated for an average pump power of 8 W at a pulse repetition frequency (PRF) of 10 kHz. This approach of simultaneous OPO+DFG process can be employed to significantly enhance the idler generation efficiency of nanosecond OPOs.

Compact and Highly Efficient Passively Q-Switched Intracavity KTA-OPO at 1.53 and 3.47 μm

Both the signal (1.53 μm) and idler (3.47 μm) performances of a KTA-based optical parametric oscillator (OPO) are presented. The KTA-OPO is intracavity driven by a diode-pumped Nd:YV04/Cr:YAG passively Q-switched laser with a quite compact configuration. The signal and idler average output powers up to 941 and 583 mW, respectively, have been achieved, corresponding to an improved diode-to-idler conversion efficiency of 6.5% and a diode-to-OPO (signal+idler) conversion efficiency of 16.9%. At different pump levels, the signal pulse duration and repetition rate are detected to be in the range of 1.8–3.2 ns and 13–112 kHz, respectively. Moreover, near diffraction limited and Gaussian type beam profiles at 1.53 and 3.47 μm are also observed.

Observation of four-wave mixing in slow-light silicon photonic crystal waveguides

Four-wave mixing is observed in a silicon W1 photonic crystal waveguide. The dispersion dependence of the idler conversion efficiency is measured and shown to be enhanced at wavelengths exhibiting slow group velocities. A 12-dB increase in the conversion efficiency is observed. Concurrently, a decrease in the conversion bandwidth is observed due to the increase in group velocity dispersion in the slow-light regime. The experimentally observed conversion efficiencies agree with the numerically modeled results.

Efficient Long Wave IR Laser from Ho:YAG 2 μm Pumped ZnGeP2 Optical Parametric Oscillator

An efficient high power long wave infrared laser based on ZnGeP2 optical parametric oscillator pumped by a 2.09 μm Tm:YLF/Ho:YAG laser at 10KHz pulse repetition rate is reported. The pump to idler conversion efficiency is 8% at 15.6 W Ho pump power level and a quantum efficiency of 31 % when the 1'idler wavelength is tuned at 8.08 μm. The wavelength tuning range from 8–9.1 μm is also achieved by rotating the ZGP crystal.

Parametric amplification and wavelength conversion in the 1040–1090 nm band by use of a photonic crystal fiber

Highly efficient parametric amplification and wavelength conversion have been demonstrated in the 1040–1090 nm band. A nonlinear photonic crystal fiber was used to provide the anomalous dispersion required for phase matching at 1 μm. A 40 dB maximum gain and +35 dB idler conversion efficiency have been achieved in the subnanosecond pulsed regime and by using a spectrally filtered supercontinuum source as a small signal.

Widely tunable picosecond optical parametric generation and amplification in BiB3O6

Efficient generation of widely tunable picosecond pulses from the visible to near-infrared is demonstrated by optical parametric generation and amplification in BiB(3)O(6). Pumped by the second harmonic of an amplified mode-locked Nd:YAG laser at 532 nm, also generated in BiB(3)O(6), a signal and idler tuning range of 740-1893 nm has been achieved with angle tuning under type I (o?e+e) phase-matching in the optical yz-plane. With 40-ps pump pulses of 420-muJ energy, single-pass signal pulse energies of up to 48.6 muJ have been obtained at total OPA pump to signal and idler conversion efficiency as high as 30%. Significant temperature tuning under type I (o?e+e) noncritical interaction along the optical z-axis is also demonstrated, extending the signal tuning range from 740 nm down to 676 nm and idler tuning range from 1893 nm up to 2497 nm. Using second harmonic generation of the amplified signal pulses, also in BiB(3)O(6),wavelength extension to 370-500 nm has been achieved at 24% conversion efficiency, providing 10-muJ pulses across the tuning range. Optical parametric generation and amplification in BiB(3)O(6) under strong two-photon absorption pumped by 210-muJ pulses at 355 nm is also reported, providing amplified signal pulse energies of 14.2 muJ at OPA conversion efficiency as high as 21% and a spectral coverage across 450-1674 nm.

Pulsed optical parametric oscillators with intracavity optical parametric amplification: a critical study

It is known that the idler conversion efficiency of optical parametric oscillators (OPOs) can be increased by adding a second nonlinear crystal in the cavity. This crystal is pumped by the signal and acts as an optical parametric amplifier (OPA) for the idler. However, this technique unavoidably increases the oscillation threshold because of additional losses and increased build-up time due to cavity lengthening. In this paper, we investigate both theoretically and experimentally the benefits and drawbacks of this so called OPO–OPA configuration versus the singly resonant OPO (SRO) configuration. Calculations are found to be in agreement with an experimental study of a SRO and an OPO–OPA operating near 3.4 μm both pumped by a 90-mJ 27-ns Nd:YAG laser. Our study reveals that the OPO–OPA needs to be driven at least two times above threshold to produce more idler energy than the SRO. In addition, near 3 μm the OPO–OPA is particularly efficient given that the difference frequency wave generated in the second crystal is also output coupled.