Yongliang Jiang

Self-referenced spectral interferometry based on self-diffraction effect

A new technique of “self-referenced spectral interferometry” is demonstrated based on a self-diffraction effect and applied to the measurement of femtosecond pulses. The reference pulse is the first-order self-diffraction pulse that is generated in a thin bulk medium by the self-diffraction process from the incident pulses. A proof-of-principle experiment succeeded in characterizing a ∼55 fs pulse at 800 nm and a sub-10 fs pulse at 400 nm. The system can be simultaneously used to measure ultrashort pulses by the self-diffraction based on frequency-resolved optical gating.

Sub-15fs ultraviolet pulses generated by achromatic phase-matching sum-frequency mixing

17.4fs ultraviolet pulses with >400nJ were generated by achromatic sum frequency mixing of 805nm pulses and ultra-broadband visible pulses. Angular dispersion was introduced to achieve broadband phase-matching by a prism pair.

Transient-grating self-referenced spectral interferometry for infrared femtosecond pulse characterization

We propose a technique for measuring infrared femtosecond pulses: transient-grating self-referenced spectral interferometry. Based on this technique, we built an extremely simple, alignment-free device and successfully characterized both 38 fs pulses at 800 nm and sub-two-cycle 10 fs pulses at 1.75 μm.

Ultrabroadband noncollinear optical parametric amplification with LBO crystal

Ultrabroadband visible noncollinear optical parametric amplification (NOPA) was achieved in an LBO crystal, with a continuum seed pulse generated from a sapphire plate. The spectral bandwidth of the amplified visible pulse was about 200 nm, which can support sub-5 fs pulse amplification. An amplified output of 0.21 microJ with an average gain of about 210 was achieved. This provides, to the best of our knowledge, the first-time demonstration of such broadband amplification with a biaxial nonlinear optical crystal. Both the simulation and experimental results indicate that the LBO has a great potential as nonlinear medium in power amplifier for TW to PW noncollinear optical parametric chirped pulse amplification (NOPCPA) systems.

Spectral modulation observed in Chl-a by ultrafast laser spectroscopy

Broadband real-time dynamic vibronic coupling in Chl-a were experimentally studied using few cycle laser pulses of 6.8fs duration and a 128-channnel lock-in amplifier. Thanks to the extreme temporal resolution benefitting from the ultrashort laser pulse, the real-time modulation of the electronic transition energy induced by the molecular vibrations were calculated by the time dependent first moments of the bleaching band. The transition energy was found to be modulated periodically with the same frequencies of molecular vibration found in the Fourier amplitude spectrum of the difference absorbance real-time traces. This was interpreted to be due to the difference in the effective transition energy associated with the wavepacket motion induced by the equilibrium positions of potential curves between the ground state and the excited state. Using the values, Huang-Rhys factors for several vibrational modes involved in the spectral modulation at the room-temperature have been determined.

Characterization of infrared femtosecond pulses by using transient-grating self-referenced spectral interferometry

We propose a new technique for femtosecond pulse characterization - transient-grating self-referenced spectral interferometry. Using this technique, we built an extremely simple, alignment-free device and successfully sub-two-cycle 10-fs pulses at 1.75 μm.

Ultrabroadband visible NOPA with LBO crystal

Ultrabroadband visible noncollinear optical parametric amplification (NOPA) was achieved in a biaxial crystal. The amplified pulse has a spectral width of 200nm with energy of 0.21uJ in a 1mm thick LBO crystal.

Sub-20fs ultraviolet pulses generated by achromatic phase-matching sum frequency mixing

17.4fs ultraviolet pulses with >400nJ were generated by achromatic sum frequency mixing of 805nm pulses and ultra-broadband visible pulses. Angular dispersion was introduced to achieve broadband phase-matching by a prism pair.