Power scaling of continuous-wave second harmonic generation in a MgO:PPLN ridge waveguide and the application to a compact wavelength conversion module.

The power scaling of continuous-wave (CW) second harmonic generation (SHG) in a MgO:periodically poled lithium niobite (PPLN) ridge waveguide is investigated. The nonlinear coefficient and propagation loss factors of the MgO:PPLN waveguide are verified for future reference. The MgO:PPLN waveguide structure is determined according to a practical fiber coupling configuration, as well as the theoretical model of output power characteristics. Utilizing the designed MgO:PPLN waveguide, the 775 nm SHG power successfully reaches up to 4.02 W at an incident power of 7 W with overall conversion efficiency of 58%. Finally, a compact all-fiber waveguide conversion module is demonstrated for verifying the feasibility of commercial applications.

Forty-photon-per-pulse spectral phase retrieval by shaper-assisted modified interferometric field autocorrelation.

We retrieve the spectral phase of 400 fs pulses at 1560 nm with 5.2 aJ coupled pulse energy (40 photons) by the modified interferometric field autocorrelation method, using a pulse shaper and a 5 cm long periodically poled lithium niobate waveguide. The carrier-envelope phase control of the shaper can reduce the fringe density of the interferometric trace and permits longer lock-in time constants, achieving a sensitivity of 2.7×10(-9) mW(2) (40 times better than the previous record for self-referenced nonlinear pulse measurement). The high stability of the pulse shaper allows for accurate and reproducible measurements of complicated spectral phases.

Spectral phase retrieval of 8 fs optical pulses at 600 nm by using a collinear autocorrelator with 300-µm-thick lithium triborate crystals.

We report on noniterative spectral phase retrieval of 1.1 nJ, 8 fs pulses at 600 nm by using 300-µm-thick lithium triborate crystals in a standard collinear autocorrelator with ≈2 min data acquisition time. This method is simple, sensitive, and immune to the spectral distortion and UV absorption of the linear and nonlinear optics.

Ultrasensitive direct-field retrieval of femtosecond pulses by modified interferometric field autocorrelation.

We report on spectral phase retrieval of 50 MHz, 374 fs optical pulses at 1560 nm with 28 aJ coupled pulse energy by measuring two modified interferometric field autocorrelation traces using a 5-cm-long periodically poled lithium niobate waveguide. The corresponding sensitivity is 1.1x10(-7) mW(2), improving on the previous record by about 20 times. The same data traces can also be used to retrieve the power spectrum, given that the ratio of powers at two specific wavelengths is known.

Direct spectral phase retrieval of ultrashort pulses by double modified one-dimensional autocorrelation traces.

We propose and experimentally demonstrate an original method to analytically retrieve complete spectral phase of ultrashort pulses by measuring two modified interferometric field autocorrelation traces using thick nonlinear crystals with slightly different central phase-matching wavelengths. This new scheme requires no spectrometer, detector array, nor iterative data inversion, and is compatible with periodically poled lithium niobate (PPLN) waveguide technology offering potential for high measurement sensitivity.