Spectral broadening of a weak 80-microJ picosecond 530-nm laser pulse in a BK-7 glass has been enhanced over the entire spectral band by the presence of an intense millijoule picosecond 1060-nm laser pulse. The spectral distributions of the self-phase modulation and the induced-phase modulation signals are similar. The dominant enhancement mechanism for the induced supercontinuum was determined to be caused by an induced-phase modulation process, not by stimulated four-photon scattering.
INTRODUCTIONKnowledge of the dynamical properties of impurities and defects in crystals is indispensable for understanding the properties of semiconductors1'2.Picosecond and nonlinear spectroscopy, which has been shown to be very sensitive to defect states, has only rarely been used to study these important energy levels.In this communication most of the important picosecond and nonlinear effects in CdSe are proved to be controlled by native defects and a simple Klasens -like model shown sufficient for explaining the dynamics of this material.
STEADY -STATE MEASUREMENTS (a) METHODS AND MATERIALSFive undoped samples of CdSe, supplied by Cleveland Crystals, Inc., three made semi -insulating (SI) by annealing with Se vapor (samples denoted here by the label H1,H2, and H3) and two n-type(samples denoted here by the label L1 and L2), were studied by photoluminescence and absorption spectroscopy.Sample H1 was 2 mm thick, while samples H2 and H3 were 1.55 mm thick.Samples H2 and L1 had their optical é axes parallel to the surface for polarization studies.The c axis of the other samples were perpendicular to the surface. The low-resistivity samplesyLl and L2, were only studied by photoluminescence in order to show that their dynamics are different from the dynamics of the high-resistivity samples.The excitation laser (at wavelength 488 nm) was focused to an intensity of ,105 W /cm2 at maximum and the excitation power was varied using neutral density filters. At 77 K, the photoluminescence spectra of each sample consisted of two major bands3. The photoluminescence spectra is displayed in Fig. 1 for the high resistivity samples at 77 K.The free-carrier band (XH band) ,which peaked at 682 nm, showed conduction-(,)-15 F-Z m cc r Ñ 10 z w z 5 0 650 670 690 710 WAVELENGTH (nm) 730 750 770 FIG 1: Luminescence spectra of semi -insulating samples of CdSe (three samples) at 77 K, showing the XH and XA bands. Sample H1 at 77 K(-.-.), sample H2 at 77 K(---), sample H3 at 77 K(---) .electron -to -hole (CH) transitions and shallow-donor -to -hole (DH) transitions. The other broad band (XA band) which peaked at 720 nm, shows both electron -to-shallow acceptor (CA) and shallow-donor -to acceptor (DA) transitions3.As the temperature was raised SP /E Vol. 524 Spectroscopic Characterization Techniques for Semiconductor Technology 11 (1985) / 95
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.