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Recently scientists have made considerable progress in using optical phase to control physical, chemical and biological processes. In a collaboration between the University of Toronto and the University of Iowa, we have shown how optical phase can be used to control electron density and currents as well as spin density and spin currents in bulk (3-D) or quantum well (2-D) semiconductors as well as...
Using the unique characteristics of multiphoton ionization with focused femtosecond pulses, we report on a pump and probe metrology to analyze carrier dynamics inside dielectrics. We characterize the sub-picosecond trapping of carriers inside fused SiO2.
By repeated optical breakdown with focused femtosecond pulses, we decrease the refractive index of fused silica by few percent. The subsequent micro-lens formation is associated with a reduction of multiphoton absorption in all dielectrics.
Waveguides were written in glass using the femtosecond laser direct-write technique. The refractive index changes induced were found to be polarization dependent. We propose that photo-ionization rates are the origin of this polarization dependence.
Ultrafast density-dependent optical spectroscopic measurements on a quantum dots-in-a-well heterostructure reveal several distinctive phenomena, most notably a strong coupling between the quantum well population and light absorption at the quantum dot excited state.
Using a two stage, white-light seeded, collinear, femtosecond optical parametric amplifier based on BIBO crystal, sub-30-fs signal pulses with energies exceeding 200-muJ, corresponding to 5-fold pulse shortening and ~30% internal conversion efficiency, are generated.
We have used terahertz time-domain spectroscopy to investigate carrier dynamics in a wide range of semiconductors. The technique allows discriminating between free charges and excitons and is perfectly suitable to study carrier-carrier interactions in nanostructured materials.
New type of non-volatile high-speed optical memory is proposed, which utilize the magnetization reversal of nanomagnet by spin-polarized photo-excited electrons. To verify high speed of proposed demultiplexing method, the switching of spin polarization at 2.2 TGz was demonstrated.
Pulse compression in a differentially pumped gas-filled hollow-fiber was used to generate compressed laser pulses of 1.2 mJ at 3.7 fs, corresponding to 1.5-cycle, 0.3-TW output, from positively chirped 33-fs laser pulses.
We review the basic principles of the femtosecond laser direct writing approach. This technology opens the possibility to specifically tune the light evolution in the linear as well as in the nonlinear regime.
Femtosecond laser-written active waveguide devices, namely waveguide amplifiers and DFB waveguide lasers were fabricated in doped phosphate glasses. Gain was achieved across the complete C-band and a laser with output power of 102 mW was demonstrated.
Intersubband cavity polaritons in a quantum well waveguide structure are photogenerated by 12-fs near-infrared pulses. Multi-THz transients trace the non-adiabatic switch-on of ultrastrong light-matter coupling and the conversion of bare photons into cavity polaritons.
We use dual-quadrature spectral interferometry to demonstrate single shot amplitude and phase retrieval of shaped waveforms generated from a 10 GHz optical frequency comb and switched at the repetition rate of the frequency comb.
We present the theory and experimental realization of simultaneously localized and strongly coupled optical and mechanical modes in periodic nanostructures. The mechanical properties of localized phonons with Gigahertz frequencies and sub-picogram masses are studied via all-optical measurements.
A frequency comb is phase-locked to a CW laser with an electro-optic-modulator providing 1.6 MHz feedback bandwidth. Residual phase noise is as low as -94 dBc/Hz, and the comb remained locked under mechanical vibration of up to 1.9 g.
The distribution of an ultrafast optical pulse train over multiple fiber links with long-term stable timing precision within 2 femtoseconds rms is accomplished by integrating a polarization maintaining output with 300 meter long fiber links.
The second-order coherence properties of highly-incoherent cw sources (true blackbody and amplified spontaneous emission) are directly evidenced at femtosecond timescales by use of an interferometric autocorrelator based on a two-photon absorption in a GaAs phototube.
The combination of collinear time-resolved two-dimensional spectroscopy and field-resolved detection allows for the measurement of optical nonlinearities of arbitrary order. Results are presented for intersubband transitions in a multiple quantum well sample.
We demonstrate a simple experimental technique to perform optical Two-Dimensional Fourier Transform Spectroscopy. This technique derives from a modified pump-probe geometry with a pair of collinear, phase-locked pump pulses.
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