Optical Parametric Conversion Research Articles

Impact of pump-phase noise in PPLN-based optical parametric amplifier and wavelength converter for digital coherent transmission

Wideband signal amplification and optical signal processing with a high gain using an optical parametric amplifier based on a periodically poled LiNbO3 (PPLN) waveguide is attractive for constructing wideband optical fiber networks. We experimentally investigate the transfer characteristics of the phase noise of a pump laser in χ(2)-based optical parametric amplification and wavelength conversion on the basis of second-harmonic-generation and differential-frequency-generation processes. We also evaluate the effect of the transferred phase noise on signal quality in dispersion-unmanaged digital coherent fiber transmission systems. We show that the phase noise is transferred only to the wavelength-converted idler and does not affect the amplified signal even by using a pump laser with a MHz-order linewidth. We also show that the phase noise transferred to the idler light can have a similar impact on signal quality as equalization-enhanced phase noise (EEPN) in digital coherent transmission. The signal penalty including EEPN was evaluated with several pump lasers and at symbol rates of 32, 64, and 96 Gbaud. We also propose a method of using correlated pump lights between a wavelength converter pair to cancel out the transfer of phase noise.

A topological nonlinear parametric amplifier

Topological boundary states are well localized eigenstates at the boundary between two different bulk topologies. As long as bulk topology is preserved, the topological boundary mode will endure. Here, we report topological nonlinear parametric amplification of light in a dimerized coupled waveguide system based on the Su-Schrieffer-Heeger model with a domain wall. The good linear transmission properties of the topological waveguide arising from the strong localization of light to the topological boundary is demonstrated through successful high-speed transmission of 30 Gb/s non-return-to-zero and 56 Gb/s pulse amplitude 4-level data. The strong localization of a co-propagating pump and probe to the boundary waveguide is harnessed for efficient, low power optical parametric amplification and wavelength conversion. A nonlinear tuning mechanism is shown to induce chiral symmetry breaking in the topological waveguide, demonstrating a pathway in which Kerr nonlinearities may be applied to tune the topological boundary mode and control the transition to bulk states.

THERMALLY INDUCED BIREFRINGENCE AND MODE SELECTION IN CAVITY OF PASSIVELY Q-SWITCHED DIODE PUMPED Nd:YAG LASER

Operating regimes of an optical system consisted of compact pulsed master diode-pumped Q-switched Nd:YAG laser and triple-crystal (KTP) ring cell of the optical parametric oscillator have been investigated. It has been experimentally shown that frequency-selective properties of a passive Q-switched unit in the “natural mode selection” are enhanced by creating a polarization interference filter Lyot with the phase plate in the form of a laser active element with the thermally induced birefringence and a polarizer. Such filter Lyot appears in the Nd:YAG laser cavity during operation at relatively high energy and repetition rate of radiation pulses (60–100 mJ, 20 Hz). The combined action of the “natural mode selection” process and the Lyot filter ensures the stable operation of a passive Q-switched Nd:YAG laser in the single frequency lasing mode (the lasing bandwidth is less than 57 MHz). The master single frequency pulsed Nd:YAG laser (λ = 1.06 μm) allows reducing the energy of pulses applied to the input of the optical parametric oscillator by more than 1.5 times while maintaining the specified energy level of the output pulses (30 mJ, λ = 1.57 μm). An additional increase in the efficiency of the optical parametric oscillator conversion is achieved by introducing
 a two-lens 1.3x telescope into the master laser cavity.

Theoretical and experimental study on gain competition adjustment of intracavity pumped dual-wavelength optical parametric oscillator using an aperiodically poled lithium niobate at approximately 3.30 and 3.84 μm

An intracavity pumped dual-wavelength optical parametric oscillator based on a single MgO:APLN crystal at approximately 3.30 and 3.84 μm was studied using a folded-type double cavity, which consists of a 1.06 μm resonator and dual-wavelength optical parametric oscillator. With the maximum incident diode power of 43.84 W, the maximum output powers of 1.43 W at 3.30 μm and 2.47 W at 3.84 μm were obtained under T = 70%@1.57 μm and T = 25%@1.47 μm at a repetition rate of 40 kHz, corresponding to conversion efficiencies of 3.26% and 5.63%, respectively. The pulse widths of 11.35 ns at 3.30 μm and 13.17 ns at 3.84 μm were obtained synchronously. A dual-wavelength optical parametric energy conversion model was set up to simulate the influence of the transmittance at resonant signal wavelengths on the output power of idler wavelengths. Both theoretical and experimental results demonstrated that the relationships in output power between 3.30 and 3.84 μm can be affected by adjusting the transmittance at signal wavelengths.

Single-Photon Infrared Imaging With a Silicon Camera Based on Long-Wavelength-Pumping Two-Photon Absorption

We experimentally demonstrated an ultra-sensitive imaging system for telecom photons based on the non-degenerate two-photon absorption in a silicon-based electron multiplying charge-coupled device (EMCCD). The proposed long-wavelength-pumping scheme with mid-infrared pulsed excitation could not only effectively increase the two-photon absorption coefficient, but also significantly suppress the background noise caused by the harmonic absorption of the strong pumping field. In comparison to the photoelectric response via the degenerate two-photon absorption, the implemented configuration could offer over 30-folded enhancement of the photon-counting rate in the infrared imaging. The resulting detection sensitivity up to 1 photon/pixel/pulse was unprecedentedly approached, thus facilitating the single-photon operation. The elimination of the stringent phase matching as typically required in the optical parametric conversion has led to a high spatial resolution of 13 μm. Moreover, the on-chip nonlinearity of the optical imager would enable a broadband spectral window and an enlarged field of view. In combination with the 5-ps temporal resolution due to the coincident optical gating, the presented imaging system would find various promising applications, such as low-light fluorescence lifetime microscopy and photon counting time-of-flight 3D imaging.

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.

High-power widely tunable all-fiber thulium-assisted optical parametric oscillator at SWIR band.

A novel short-wave infrared (SWIR) all-fiber thulium-assisted optical parametric oscillator (TAOPO) that exploits jointly optical parametric conversion and thulium amplification in a highly nonlinear fiber (HNLF) and thulium-doped fiber (TDF) is demonstrated. This is implemented through constructing a joint fiber line by directly fusion splicing 50 m HNLF with 1.5 m TDF. Incorporating a bidirectional-pumping scheme, i.e., forward-pumped by a step-tuned C-band pulsed laser, and simultaneously backward-pumped by an L-band continuous-wave laser, this TAOPO produces a pulsed SWIR laser at output power higher than 200 mW, signal-to-noise ratio over 40 dB, and wavelength tuning range beyond 150 nm from 1815 to 1968 nm. Via separate characterization of the HNLF and TDF joint fiber line, the tunability of the current TAOPO to shorter wavelength is only limited by the employed fiber components, while higher power could be realized by increasing the backward pump power. This TAOPO could be a promising platform for the generation of a highly functional SWIR source that facilitates applications such as bond-selective imaging of deep tissue.

High-Brightness Continuously Tunable Narrowband Subterahertz Wave Generation

We report on the generation of high-brightness (high peak power and narrow linewidth) continuously tunable subterahertz waves by optical parametric wavelength conversion using lithium niobate as a nonlinear optical crystal. The high-brightness subterahertz waves were achieved by expanding the interaction volume of the pumping beam and the idler wave, as well as the subterahertz wave, during wavelength conversion and by injecting the seeding beam into the idler wave. We could continuously tune the wavelengths of the generated subterahertz waves by controlling the angle and wavelength difference between the pumping and injection seeding beams to satisfy the noncollinear phase-matching conditions. The high-brightness (maximum peak output power, linewidth) and tunable range were about 10 MW/sr· cm 2 (>7 kW, <;5 GHz), and 760-150 μm (0.39-2 THz), respectively.

Investigation of optical property in LiInSe2 single crystal grown by Bridgman Stockbarger method using stepper translations for mid IR laser application

Abstract LiInSe 2 polycrystalline material was synthesized in a horizontal muffle furnace with the help of a mechanical motor. LiInSe 2 single crystal has successfully been grown by modified Bridgman furnace using stepper translation. The grown crystal was subjected to various characterizations such as Powder X-ray Diffraction (XRD), Single crystal X-ray Diffraction, High Resolution X-ray Diffraction (HRXRD), Fourier transform infrared spectroscopy (FTIR), Ultraviolet–Visible-Near Infrared spectroscopy (UV–Vis–NIR), Photoluminescence and Micro Raman spectroscopy. The grown LiInSe 2 crystal was confirmed by single crystal and powder X-ray diffraction analyses. The FTIR transmission of grown LiInSe 2 single crystal was found to be around 80% which is being used in the field of mid Infrared laser, Lidar sensor, and optical parametric conversion. The band gap energy 1.85 eV was calculated from absorption spectrum. The cut off wave length is 617 nm for LiInSe 2. The photoluminescence spectrum was observed around 598 nm at ambient temperature, corresponding energy is 2.07 eV. The structural and compositional uniformities of LiInSe 2 were studied using micro-Raman scattering spectroscopy at room temperature. The insignificant change in the Full width at half maximum (FWHM) of the Г 1 ( W 1 ) measured at different regions of the crystal further reveals that the composition throughout its length is fairly uniform.

Experimental demonstration of nanosecond optical parametric amplifier in YCOB

In this letter, we provide the experimental demonstration of nanosecond optical parametric amplification in YCOB centered at 1572 nm. The optical gain characterization of YCOB crystal was simulated and tested in this optical parametric conversion. A saturated OPA gain of 2.4 was obtained. The results confirm that YCOB crystal has the potential to be used in a high-energy cascade of MOPA parametric amplifiers at 1572 nm.

Novel Optical Parametric Amplifier at 1572 nm Wavelength Using KTP Crystal

A novel master oscillator/power amplifier architecture for optical parametric conversion of high pulse energy from 1.064 μm to 1.572 μm in KTiOPO4 crystal is presented. A high gain of more than 80 at 1.572 μm pumped by a high energy Q-switched pulse laser is realized. With a seeding signal energy of 1 mJ, and 400 mJ pump pulse at 100 Hz, an amplified signal pulse energy of over 80 mJ is obtained. The total optical-optical conversion efficiency reaches 21%.

Optical parametric wavelength conversion for 53.5-Gb/s RZ-DPSK signal with phase preserved amplitude regeneration

We demonstrated the wavelength conversion for a 53.5-Gb/s RZ-DPSK signal with 1-dB parametric gain and phase preserved amplitude regeneration. The parametric wavelength conversion is based on four-wave mixing in a highly nonlinear fiber with a pulse pump. The wavelength converted and regenerated signal shows improved optical signal-to-noise ratio and bit-error-rate (BER) performances compared to the degraded signal. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2172–2175, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27034

基于YCOB晶体分析信号光脉冲时间特性对光参变啁啾脉冲放大光谱和转换效率的影响

基于YCOB晶体分析信号光脉冲时间特性对光参变啁啾脉冲放大光谱和转换效率的影响

Broadband stimulated four-wave parametric conversion on a tantalum pentoxide photonic chip

We exploit the large third order nonlinear susceptibility (χ(3) or "Chi 3") of tantalum pentoxide (Ta(2)O(5)) planar waveguides and realize broadband optical parametric conversion on-chip. We use a co-linear pump-probe configuration and observe stimulated four wave parametric conversion when seeding either in the visible or the infrared. Pumping at 800 nm we observe parametric conversion over a broad spectral range with the parametric idler output spanning from 1200 nm to 1600 nm in infrared wavelengths and from 555 nm to 600 nm in visible wavelengths. Our demonstration of on-chip stimulated four wave parametric conversion introduces Ta(2)O(5) as a novel material for broadband integrated nonlinear photonic circuit applications.

Femtosecond optical parametric conversion properties based on the BiB3O

Parametric properties in femtosecond optical parametric conversion process based on the new nonlinear crystal BiB3O6 (BIBO) are studied. The phase- matching conditions and effective nonlinear coefficients in the three principal optical planes of the BIBO crystal are calculated, optimum principal optical planes and phase -matching types are determined when using the fundamental frequency and the frequency doubling of the KLM Ti:sapphire laser as pump respectively, and temporal walk-off and spatial walk-off of three waves, and signal parametric gain and bandwidth are analyzed. We thereby provided a theoretical basis and experimental guide for obtaining the light source with high energy, wide tuning range, and short duration with femtosecond optical parametric technology based on the BIBO.

Analysis on spectral gain characteristics of PPMgLN based quasi-phase-matching optical parametric amplification

A deep understanding of the spectral gain characteristics of optical parametric oscillators (OPOs) and optical parametric amplifiers (OPAs) is important for a highly efficient optical parametric conversion. We numerically calculated the spectral gain characteristics of a quasi-phase-matching (QPM) parametric conversion process using the periodically poled 6% (mol/mol) MgO doped LiNbO3 (PPMgLN) as the nonlinear crystal. In the simulation we utilized the approach of a transformative matrix of the periodically poled nonlinear medium, which results from the small-signal approximation of three-wave mixed nonlinear equations. Numerical simulation results show that: (1) The full width at half maximum (FWHM) of the spectral gain of the parametric process becomes wider with the increase of parametric wavelength and reaches the maximum at degeneration; (2) The gain coefficient decreases gradually with the increase of parametric wavelength; (3) The spectral gain bandwidth decreases correspondingly with the increase of the nonlinear material length; (4) There exists an optimal parametric wavelength band, which is most suitable for the high gain parametric conversion when pumped by a laser source with a wide wavelength band, such as the high power fiber laser.

730-nm optical parametric conversion from near- to short-wave infrared band

A record 730 nm parametric conversion in silica fiber from the near-infrared to the short-wave infrared band is reported and analyzed. A parametric gain in excess of 30 dB was measured for a signal at 1300 nm (with corresponding idler at 2030 nm). This conversion was performed in a travelling single-pass one-pump parametric architecture and high efficiency is achieved by a combination of high peak power and a nonlinear fiber with a reduced fourth-order dispersion coefficient.

Theoretical analysis of noncollinear phase-matched optical parametric generation in BBO crystal

In this article we propose a theoretical treatment of noncollinear phase-matched femtosecond parametric interaction process pumped by ultrashort optical pulses, and investigated the pulse characteristics of OPG in BBO crystal. The results show that the major factors, which affect the optical parametric conversion coefficient and durations of the pulses, are the group velocity mismatch and the phase mismatch among the three ultra-short pulses. In addition, the material dispersion can cause the durations of the pulses to increase when pump pulse is below 20 fs , and its influence becomes more obvious at low pump intensity.

Limited efficiency of a silver selenogallate optical parametric oscillator caused by two-photon absorption

The nonresonant two-photon absorption (TPA) coefficient in silver selenogallate (AgGaSe(2)) crystals was measured for both ordinary and extraordinary polarizations in the 1300-1600-nm wavelength range. We found a cutoff wavelength for the TPA at between 1400 and 1500 nm, which corresponds to half of the bandgap energy of the AgGaSe(2) crystal. Below the cutoff wavelength we measured the TPA coefficient to be approximately 0.035 cm/MW for the extraordinary polarization and two to three times lower for the ordinary polarization. We compared the AgGaSe(2) samples from two manufacturers and observed a factor of 2 difference in the TPA coefficients. Because of the high TPA, the 1.32-mum pumped AgGaSe(2) optical parametric oscillator conversion efficiency was clipped at a low level.

Modeling and experimental observation of parametric processes in segmented KTiOPO4 channel waveguides

This letter presents a modeling technique for quasiphase-matched parametric processes in segmented channel waveguides and the results of measurements of infrared parametric fluorescence in segmented KTiOPO4 channel waveguides. We demonstrate both theoretically and experimentally a strong dependence of optical parametric oscillator tuning curves and parametric conversion efficiency (parametric gain) on the segmentation duty cycle. We show that the optimum conversion efficiency for parametric interactions in segmented waveguides is obtained for duty cycles greater than 50%. Our results validate the use of an effective continuous waveguide model for segmented channel waveguide calculations over a wide range of wavelengths and duty cycles.