Zhi-Ming Hsieh

Synthesis and measurement of ultrafast waveforms from five discrete optical harmonics.

Optical fields have been manipulated like radio frequencies into sawtooth and square-wave patterns. Achieving the control of light fields in a manner similar in sophistication to the control of electromagnetic fields in the microwave and radiofrequency regimes has been a major challenge in optical physics research. We manipulated the phase and amplitude of five discrete harmonics spanning the blue to mid-infrared frequencies to produce instantaneous optical fields in the shape of square, sawtooth, and subcycle sine and cosine pulses at a repetition rate of 125 terahertz. Furthermore, we developed an all-optical shaper-assisted linear cross-correlation technique to retrieve these fields and thereby verified their shapes and confirmed the critical role of carrier-envelope phase in Fourier synthesis of optical waveforms.

Compact optical function generator

We demonstrate the use of a nonlinear photonic crystal to generate a harmonic comb and an ultrabroad-band acousto-optic modulator for the field amplitudes and phases of the comb to succeed in synthesizing femtosecond and subfemtosecond optical field waveforms. Nonsinusoidal fields of various shapes are synthesized and verified using shaper-assisted linear cross-correlation. The compact all-solid-state system could lead to the realization of a portable arbitrary optical waveform synthesizer that is analogous in many aspects to an RF function generator.

Pulse shaper assisted characterization of single-cycle optical pulses

Shaper-assisted autocorrelation is developed to characterize single-cycle pulses. The correlation signal show significantly improved signal-to-noise ratio and thus accuracy in pulse characterization when compared to cross-correlation obtained by splitting the spectral components of the pulse.

Full control of the carrier-envelope phase of Raman-generated single-cycle waveforms

Precise control of the carrier-envelope phase of Raman genearated ultrashort pulses is achieved by generating a Raman frequency comb using an infrared laser pulse and its second harmonic to drive the Raman coherence.

Spatial light modulator for pulse-shaping of single-cycle optical pulses

A liquid crystal spatial light modulator that operates from the ultraviolet (350nm) to the mid-infrared (2400nm) is described. The modulator is suitable for shaping the electromagnetic wave form of multioctave optical pulses.

Optical function generator based on cascaded nonlinear mixing in a photonic crystal

We report the synthesis of femtosecond and subfemtosecond optical field waveforms using a frequency comb consisting of the first five harmonic components of a laser. The comb components are generated in a nonlinear photonic crystal An acousto-optic modulator is used for amplitude and phase control. We synthesized the electric field into specific electric field shapes, i.e. sub-cycle cosine, sawtooth, and squares, and checked the shapes through shaper-assisted linear cross-correlation. This development of arbitrary optical waveforms is a major step toward achieving the optical analog of a RF function generator. With these optical waveforms, nanoscopic control of electronic motion in atoms, molecules and matter could be realized.

Synthesis and measurement of ultrafast optical waveforms

Periodic femtosecond and subfemtosecond optical waveforms whose instantaneous electric fields are shaped in the form of sawtooth, square, or sub-cycle cosine and sine pulses are synthesized and are verified by a novel correlation technique.

Synthesis and Characterization of Optical Field Waveform

Periodic optical fields in the shapes of sawtooth, square, single-cycle sine and cosine are synthesized from laser harmonics generated by molecular modulation and measured using shaper-assisted cross-correlation.

Synthesis of attosecond waveforms using Raman-generated frequency combs

Attosecond optical waveforms of arbitrary shape are synthesized and verified using a Raman-generated comb of frequencies that have a controlled and stable carrier-envelope phase.

Synthesis of Subfemtosecond Periodic Waveforms

Periodic optical waveforms of arbitrary shape in the femtosecond and subfemtosecond time scale are synthesized from a comb generated by molecular modulation.