Direct detection of ultrafast thermal transients by use of a chirped, supercontinuum white-light pulse

Method of ultrafast beam rotation for single-shot, time-resolved measurements

Ultrafast optical beam rotation is proposed for single-shot, time-resolved measurements. A pump-probe configuration is considered using a diffraction grating and focusing optics to create angular encoding of the time delay between the pump and probe pulses. The characteristic time t(ap) of the grating-lens system is derived as a function of dispersion, NA, and time window T. An analytical equation for time resolution is obtained that incorporates t(ap)laser pulse width, and beam crossing, enabling optimum selection of optical components. For commercial standard gratings with width W≤50 mm, laser λ=800 nm, and NA=.05, a 160 ps time window can be achieved, and t(ap)=23 fs for T=1 ps.

Acquisition of gated spectra from a supercontinuum using ultrafast optical Kerr gate of lead phthalocyanine-doped hybrid glasses

We demonstrated the selection of the chirped supercontinuum using an ultrafast optical Kerr gate (OKG) of lead phthalocyanine (PbPc)- doped hybrid glasses. Using the OKG, narrow bandwidth and symmetrical gated spectra were obtained continuously from the chirped supercontinuum generated in a sapphire plate with a femtosecond laser. Experimental results show that the obtained Kerr-gated spectra using the PbPc-glass have many advantages comparing with that using CS(2).

Narrowband generation of ultrafast acoustic and thermal transients in thin films for enhanced detectability

A technique for the narrowband generation of ultrafast acoustic and thermal transients in thin films is demonstrated; this technique allows for enhanced detectability of these transients. The approach pursued uses a reduced-bandwidth, optical pulse train for excitation that is constructed from a series of time-delayed pulses derived from a single-laser pulse. The underlying physical limitations of this approach are considered in order to assess conditions under which successful bandwidth reduction can be realized. Results in an aluminum thin film on a tungsten-carbide substrate show successful generation and detection of a narrowband acoustic signal centered at 32.34 GHz.