Liquid interfaces play a fundamental role in science and technology. The development of surface-sensitive probes capable of yielding molecular information about these interfaces is of great importance. This paper gives an overview of our and some others' recent work on vibrational spectroscopy of liquid interfaces by the sum-frequency generation (SFG) technique. This technique, being highly surface specific and applicable to all interfaces accessible by light, has been proven to be a most powerful analytical tool for liquid interfaces. A wide range of systems have been studied including neat liquid surfaces, solid/liquid and liquid/liquid interfaces, surfactants at liquid interfaces, and electrochemical interfaces. In many cases, SFG is shown to be the only technique available that can provide detailed information about a liquid interface at the molecular level.

Liquid interfaces: A study by sum-frequency vibrational spectroscopy

Properties of gallium selenide single crystal

INTERSUBBAND RELAXATION IN GaAs/Al x Ga 1-x As QUANTUM WELL STRUCTURES

Sum-frequency vibrational spectroscopy at the liquid—air interface of methanol. Water solutions

Broadly tunable 30-fs pulses have been generated by parametric amplification of a white-light continuum at kilohertz repetition rates.

Broadly tunable 30-fs pulses produced by optical parametric amplification

Parametric three-photon interaction provides continuously tunable ultrashort pulses in extended spectral regions from the UV to the mid-IR. We focus on parametric systems operating in the pulsed mode. Optical parametric oscillators pumped by intense microsecond trains of subpicosecond pulses exhibit favorable properties. We present data on a pulsed optical parametric oscillator that has a wide tuning range from 0.7 to 1.8 μm, a conversion efficiency of a few percent, and a minimum pulse duration of as low as 65 fs. Larger tuning ranges are covered by subsequent downconversion or parametric amplification. We discuss the generation of ≲1-ps pulses at wavelengths between 2 and 18 μm. Finally, the potential of parametrically generated IR pulses is demonstrated by several applications.

K. Wolfrum

Papers

Parametric generation of femtosecond and picosecond pulses for spectroscopic applications

Intense bandwidth- and diffraction-limited picosecond pulses with large tuning range

Feedback-controlled mode-locking operation of a Nd:YLF laser at 1.047 μm