Quasi-phase Matching Wavelength Research Articles

Broadband quasi-phase-matching in dispersion-engineered all-optically poled silicon nitride waveguides

Quasi-phase-matching (QPM) has become one of the most common approaches for increasing the efficiency of nonlinear three-wave mixing processes in integrated photonic circuits. Here, we provide a study of dispersion engineering of QPM second-harmonic (SH) generation in stoichiometric silicon nitride ( Si 3 N 4 ) waveguides. We apply waveguide design and lithographic control in combination with the all-optical poling technique to study the QPM properties and shape the waveguide dispersion for broadband spectral conversion efficiency inside Si 3 N 4 waveguides. By meeting the requirements for maximal bandwidth of the conversion efficiency spectrum, we demonstrate that group-velocity matching of the pump and SH is simultaneously satisfied, resulting in efficient SH generation from ultrashort optical pulses. The latter is employed for retrieving a carrier-envelope-offset frequency of a frequency comb by using an f − 2 f interferometric technique, where supercontinuum and SH of a femtosecond pulse are generated in Si 3 N 4 waveguides. Finally, we show that the waveguide dispersion determines the QPM wavelength variation magnitude and sign due to the thermo-optic effect.

2 W quasi-white-light based on idler-resonant optical parametric oscillation cascading sum-frequency generation with PPSLT

We present a high power red-green-blue (RGB) laser light source based on cascaded quasi-phasematched wavelength conversions in a single stoichiometric lithium tantalate. The superiority of the experimental setup is: the facula of the incident beam is elliptical to increase interaction volume, and the cavity was an idler resonant configuration for realizing more efficient red and blue light output. An average power of 2 W of quasi-white-light was obtained by proper combination of the RGB three colors. The conversion efficiency for the power of the quasi-white-light over pump power reached 36%. This efficiency and powerful RGB laser light source has potential applications in laser-based projection display et al.

Experimental research on frequency doubling in periodically poled KTiOPO4 waveguide fabricated by femtosecond laser

We present in this paper the fabrication and characterization of type II waveguide in c-cut periodically poled KTiOPO4 crystal. The waveguide was fabricated by using a femtosecond laser，and the fabrication process was optimized. In our experiments single mode propagation was observed at optimal waveguide width of 145 μm and quasi-phase matching wavelength of 1064 nm. The second-harmonic conversion efficiency of 398% can be achieved.

Study of quasi-phase matching wavelength acceptance bandwidth for periodically poled LiNbO 3 crystal-based difference-frequency generation

The temperature tuning characteristics of quasi-phase matching (QPM) wavelength acceptance bandwidth in a uniform periodically poled lithium niobate (PPLN) based on difference-frequency generation (DFG) are studied theoretically and experimentally. This paper proposes a PPLN device consisting of several segments of different temperatures to obtain a more desirable performance for the QPM-DFG. The result shows that through the tuning of temperature, the bandwidth can be changed considerably and the method was proved suitable and accurate to calculate QPM wavelength acceptance bandwidth of DFG in a uniform PPLN crystal for temperatures between room temperature and 180 °C and mid-infrared (mid-IR) wavelengths ranging from 2.8 to 4.8 μm.

Fabrication and characterization of periodically poled lithium niobate waveguide using femtosecond laser pulses

We present in this letter the fabrication and characterization of thermally stable type II waveguides in Z-cut periodically poled lithium niobate crystals. The waveguides were fabricated by using a femtosecond laser and were utilized for second harmonic generation. Our experiments have shown that a quasiphase matching wavelength of 1548.2nm, a tuning bandwidth of 2nm, and a tuning temperature range of 150.4±1.6°C can be achieved.

Planar glass devices for efficient periodic poling

We demonstrate that frequency-converting devices of high quality can be realised with glass poling. The devices, made with silica-on-silicon technology, are poled with periodic, embedded electrodes, and used for second-harmonic generation. We obtain precise control of the quasi phase-matching wavelength and bandwidth, and a normalised conversion efficiency of 1.4x10-3 %/W/cm2 which, to our knowledge, is the highest obtained so far with periodic glass poling.

Retiming of picosecond pulses by a cascaded second-order nonlinear process in quasi-phase-matched LiNbO_3 waveguides

A new technique for reducing timing jitter by using a cascaded second-order nonlinear process in quasi-phase-matched (QPM) LiNbO3 waveguides is proposed. It was found that the timing jitter of a signal at QPM wavelength is not transferred to the converted pulses during cascading in a 30-mm-long LiNbO3 QPM waveguide. Timing-jitter transfer characteristics in QPM LiNbO3 waveguides are evaluated by calculation of pulse evolution, and retiming of 1.5-ps pulses in 10- and 30-mm-long waveguides is demonstrated experimentally.

Reducing photorefractive effect in periodically poled ZnO- and MgO-doped LiNbO3 wavelength converters

The photorefractive effect in annealed proton-exchanged waveguides in periodically poled nondoped, MgO- and ZnO-doped LiNbO3 was evaluated by monitoring the quasiphase matching (QPM) wavelength shift induced by a 0.784-μm-irradiating light. The QPM wavelength shift was reduced at room temperature by a factor of 3–6 in ZnO- and MgO-doped samples compared with the nondoped samples within a 104–105-W/cm2-irradiation intensity range. The doped samples exhibited no significant wavelength shifts when the temperature was raised to slightly above room temperature (50–60 °C).

Photorefractive damage of LiNbO3 quasiphase matched wavelength converters

Photorefractive damage (PRD) of LiNbO3 quasiphase matched (QPM) wavelength converters is studied by a novel two-beam method, in which the second-harmonic generation (SHG) tuning curve of a broadband probe beam is monitored. The QPM condition and wavelength conversion efficiency, which are characterized by the peak wavelength and peak intensity of the SHG tuning curve respectively, are investigated in detail with respect to the irradiation power and irradiation time. It is found that the QPM condition and wavelength conversion efficiency change markedly even for low irradiation powers (<20 mW), indicating that the PRD effect is non-negligible in LiNbO3 QPM wavelength converters intended for practical applications.

A novel method to characterize photorefractive damage in quasiphase-matched wavelength converters

A novel two-beam method is proposed and applied for the first time, to characterize photorefractive damage (PRD) in a LiNbO3 quasiphase-matched (QPM) wavelength converter. In the proposed method, irradiation light from a Ti sapphire laser and a broadband probe beam from an erbium-doped fiber amplifier are coupled into a LiNbO3 QPM waveguide. The PRD effect caused by the irradiation is studied by monitoring the generated second-harmonic light spectrum of the probe light. It is shown that PRD in the LiNbO3 QPM waveguide can be qualitatively characterized by the proposed method, and relevant information relating to the QPM wavelength conversion can be extracted directly.

Temperature and polarization dependence of LiNbO3 quasiphase-matched wavelength converters

Temperature and polarization characteristics of 1.55-μm-band LiNbO3 quasiphase-matched (QPM) wavelength converters have been studied by second-harmonic generation (SHG). It is found that the shift of the QPM wavelength is linearly proportional to temperature over the measured temperature range between 10 and 40 °C, with a temperature tolerance (corresponding to a 3 dB reduction in the QPM conversion efficiency) of greater than 10 °C for a 10-mm-long device. With respect to the angle θ of the injected fundamental light polarization direction, the SHG power changes as a function of sin4 θ, with a tolerance of over 60°. Theoretical explanations for the observed results are also presented.

Femtosecond violet light generation by quasi-phase-matched frequency doubling in optical superlattice LiNbO3

We report the 390 and 385 nm violet light generation by frequency doubling of a tunable 90 fs, 82 MHz Ti:sapphire laser in two optical superlattice LiNbO3 samples through third-order quasiphase matching (QPM). With the average incident infrared light power of 770 mW, 9.7 and 2.9 mW output second-harmonic lights were obtained without photorefractive damage. The QPM wavelength acceptance bandwidth measurement indicates that violet light generation with higher efficiency is possible.