High-efficiency Wavelength Conversion Research Articles

Wavelength conversion of KTP crystal based Stark-chirped rapid adiabatic passage

The nonlinear wavelength conversion can generate the laser wavelengths which are not directly available, thereby broadening the laser spectrum range. However, the phase mismatch greatly limits the development and application of nonlinear optical technology. The wavelength conversion schemes in a manner analogous to population transfer in atomic rapid adiabatic passage, stimulated Raman adiabatic passage (STIRAP), and Stark chirped rapid adiabatic passage (SCRAP) provide feasible solutions for efficient and broadband wavelength conversion. The SCRAP uses the Stark shift caused by the Stark field to generate energy level crossings, therefore, the population in initial state can be efficiently converted into the target state. It does not require the two-photon resonance, and can be applied to multi-photon transition. In this paper, by approximate analogy to the adiabatic population theory, a wavelength conversion model with the KTP crystals based SCRAP is established, the influence of the coupling delay parameters, width parameters, pump intensity, temperature, and incident wavelength on the conversion process are systematically studied. The results show that the signal laser energy can be almost converted into output laser energy, while the intermediate laser energy is kept extremely low in the conversion process. The conversion process is sensitive to changes in coupling delay parameters, width parameters, and pump intensity. The farther away fromits optimal value the coupling delay parameter, the lower the conversion efficiency is. When the width parameter <inline-formula><tex-math id="M1">\begin{document}$ d_2^2 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20210887_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20210887_M1.png"/></alternatives></inline-formula> is fixed, as the width parameter <inline-formula><tex-math id="M2">\begin{document}$ d_1^2 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20210887_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20210887_M2.png"/></alternatives></inline-formula> increases, the conversion efficiency first increases to a maximum value, and then slowly decreases. At the same time, the greater the value of the width parameter <inline-formula><tex-math id="M3">\begin{document}$ d_2^2 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20210887_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20210887_M3.png"/></alternatives></inline-formula>, the greater the achievable maximum conversion efficiencies, and the greater the bandwidth that can achieve high-efficiency wavelength conversion. The conversion efficiency increases as the pump intensity increases. When the conversion efficiency value reaches a maximum value, the increase in pump intensity has almost no effect on the conversion efficiency. However, changes in temperature and incident wavelength have little effect on the conversion efficiency. The above research can provide a theoretical basis for the acquisition of ultraviolet to mid-infrared light sources and the manufacture of photonic devices.

High efficiency four wave mixing and optical bistability in amorphous silicon carbide ring resonators

We demonstrate high efficiency wavelength conversion via four wave mixing in amorphous silicon carbide ring resonators with a loaded quality factor of 70 000. Owing to the high quality factor and high nonlinearity of amorphous silicon carbide, −21 dB conversion efficiency is achieved with 15 mW pump power. Moreover, the thermo-optic coefficient (TOC) of amorphous silicon carbide is measured to be 1.4 × 10−4/°C at telecommunication wavelengths. Taking advantage of the high TOC, we demonstrate optical bistability in the silicon carbide ring resonator. This work presents amorphous silicon carbide as a promising platform for applications in optical signal processing.

Broadband Wavelength Conversion Based on Parallel-Coupled Micro-Ring Resonators

We propose a broadband and high-efficiency four-wave-mixing wavelength converter based on parallel-cascaded micro-ring resonators (PCMRRs). By optimizing the distance between the mutually uncoupled ring resonators, we demonstrate that the PCMRR has a transmission spectrum with interleaved narrow and broad passbands. Broadband and high-efficiency wavelength conversion can be achieved by placing the pump and the signal in the narrow and broad passbands, respectively. We experimentally demonstrate a 25-GHz bandwidth wavelength converter based on optimally designed 3-ring PCMRR. Compared with the conventional single-ring-resonator-based wavelength converter with the same bandwidth, there is a 15-dB enhancement of conversion efficiency for the 3-ring PCMRR when the input pump power is 10 dBm.

Second harmonic generation in nano-structured thin-film lithium niobate waveguides.

Integrated thin-film lithium niobate platform has recently emerged as a promising candidate for next-generation, high-efficiency wavelength conversion systems that allow dense packaging and mass-production. Here we demonstrate efficient, phase-matched second harmonic generation in lithographically-defined thin-film lithium niobate waveguides with sub-micron dimensions. Both modal phase matching in fixed-width waveguides and quasi-phase matching in periodically grooved waveguides are theoretically proposed and experimentally demonstrated. Our low-loss (~3.0 dB/cm) nanowaveguides possess normalized conversion efficiencies as high as 41% W-1cm-2.

Efficient and broadband wavelength conversion in a slot waveguide with the periodic structure altering the phase-mismatch.

High-efficiency wavelength conversion based on the quasi-phase-matching technique is proposed and simulated in a silicon slot waveguide. Due to the tight light confinement and high nonlinear material (silicon nanocrystal) filled in the slot region, a large nonlinear coefficient of 4100/(W·m) is achieved. With the waveguide width changing alternately to manage the phase-mismatch, periodical attenuation of the idler power is suppressed even in the presence of severe dispersion. Numerical simulation shows that an efficiency of -12.3 dB at 1850nm and a 3-dB bandwidth of 484nm are available for the 1550nm wavelength pump in a 4mm long silicon slot waveguide.

Theoretical analysis of wavelength conversion through an antenna‐enhanced up‐conversion

AbstractWe theoretically investigate two‐photon up‐conversion process on a quantum dot (QD) through an optical antenna for high efficiency wavelength conversion. For a simplified one‐dimensional model, we analytically derive the propagator for the up‐conversion process, and numerically calculate the wave function of the converted photon. As a result, the up‐conversion probability can be increased up to 0.7. Because the probability for the QD only is about 0.04 in the same condition, one can see that the optical antenna clearly enhances the process. We also find the existence of the optimal regime for the antennaQD coupling constant. We discuss the origin of the optimal coupling and show that a quantum mechanical coupling between the QD and optical antenna plays an essential role for the high efficiency wavelength conversion. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

基于四波混频效应的差分相移键控信号波长转换的数值分析

We numerically investigate the main constrains for high efficiency wavelength conversion of differential phase-shift keying (DPSK) signals based on four-wave mixing (FWM) in highly nonlinear fiber (HNLF). Using multi-tone pump phase modulation techniques, high efficiency wavelength conversion of DPSK signals is achieved with the stimulated Brillouin scattering (SBS) effects effectively suppressed. Our analysis shows that there is a compromise between conversion efficiency and converted idler degradation. By optimizing the pump phase modulation configuration, the converted DPSK idler's degradation can be dramatically decreased through balancing SBS suppression and pump phase modulation degradation. Our simulation results also show that these multi-tone pump phase modulation techniques are more appropriate for the future high bit rate systems.

High efficiency and high energy parametric wavelength conversion using a large aperture periodically poled MgO:LiNbO 3

We have demonstrated an efficient high energy 2 μm laser generation with a 36 mm long large aperture 5 mol% MgO-doped periodically poled LiNbO 3 (PPMgLN) nonlinear optical crystal. A high power Q-switched Nd:YAG laser (1.064 μm) was used to pump the quasi-phase matched (QPM) optical parametric oscillator (OPO). A total output energy of 186 mJ with 58% slope efficiency was obtained in two separate beams at 2 μm.

High efficiency wavelength conversion of 10 Gb/s data in silicon waveguides

Efficient wavelength conversion via four-wave-mixing in silicon-on-isolator p-i-n waveguides has been realized. By reverse biasing the p-i-n diode structure formed along the silicon rib waveguide, the nonlinear absorption due to two photon absorption induced free carrier absorption is significantly reduced, and a wavelength conversion efficiency of -8.5 dB has been achieved in an 8 cm long waveguide at a pump intensity of 40 MW/cm2. A high-speed pseudo-random bit sequence data at 10 Gb/s rate is converted to a new wavelength channel in the C-band with clear open eye diagram and no waveform distortion. Conversion efficiency as functions of pump power, wavelength detuning, and bias voltages, have been investigated. For shorter waveguides of 1.6 cm long, a conversion bandwidth of > 30 nm was achieved.

Intracavity PPLN crystals for ultra-low-voltage laser Q-switching and high-efficiency wavelength conversion

We report to the best of our knowledge the lowest switching voltage in an electro-optically Q-switched Nd:YVO4 laser by using a 13-mm long, 14-μm-period PPLN crystal as a Pockels cell. A switching voltage as low as ∼50 V in the PPLN crystal was sufficient to hold off the lasing of the Q-switched laser at a pump power more than two times above its continuous-wave threshold. When the PPLN Q-switch was driven by a 100-V voltage at 6.5 kHz, we obtained 0.9-kW laser peak power from this 1-W diode-pumped Nd:YVO4 laser system with 13% output coupling. When the PPLN Pockels cell was cascaded with a 5-cm long, 30-μm-period PPLN crystal, we produced ∼μJ/pulse energy at 1.59 μm from optical parametric generation inside the actively Q-switched laser.

Correction to "High-efficiency wavelength conversion using FWM in an SOA integrated DFB laser"

In the above-named letter [ibid., vol. 12, pp. 31?33, Jan. 2000] reference [11] was incorrect. A correct version of [11] is provided.

High-efficiency wavelength conversion using FWM in an SOA integrated DFB laser

A wavelength converter that uses four-wave mixing (FWM) in an SOA-integrated distributed-feedback (DFB) laser was demonstrated. Lossless conversion up to 300-GHz detuning and a conversion efficiency of -5 dB at 1-THz detuning was achieved. The device exhibited low ASE (noise) level, and noise figure (NF) characteristics of 24 dB for 16-nm wavelength conversion was observed. This high-efficiency FWM wavelength conversion provided by a single device is promising for optical wavelength shifters in large-scale optical communication systems.

Low-power high-efficiency wavelength conversion based on modulational instability in high-nonlinearity fiber

Bandwidth and peak efficiency are enhanced for wavelength conversion based on induced modulation instability by use of dispersion-shifted fiber in which the nonlinearity (n(2)/A(eff)) is enhanced by a factor of ~4.5 over that of conventional dispersion-shifted fiber. We experimentally obtain a peak conversion efficiency as high as 28 dB over a 40-nm bandwidth with 600 mW of peak pump power. Considerations for further enhancement of fiber-based wavelength conversion are also discussed.

Selective Wavelength Conversion of Alexandrite Laser Emission into the First Stokes Emission in Hydrogen.

Selective and high-efficiency wavelength conversion of the fUndamental wave of tunable, high-power alexandrite laser emission into the first Stokes emission in H2 gas is reported. Soft focussing in a long Raman cell has yielded photon conversion efficiency of as high as 80% over the entire tunable range of the fundamental wavelength. An unexpected narrow spike has been occasionally observed in the depleted pump pulse transmitted through the cell. Optimization of cell length and the shape of the depleted pump pulse with and without the narrow spike are discussed in the framework of semiclassical treatment in transient regime.