Optical Kerr shutter

Kerr Shutter Experiment. The NLO properties of DEANST was also investigated through an optical Kerr shutter experiment. The optical Kerr shutter has the advantages of simple construction and fast response time. DEANST dissolves easily in many solvents. A saturated sample in a DMF (40 wt%) or in a nitrobenzene (30 wt%) was investigated in the Kerr shutter experiment. Powders of DEANST were dissolved in these solvents. The sample solution was poured into a silica glass cell of 1 mm thickness. 

Tlie usual experimental techniques developed to study the optical Kerr effect in materials have already been described in a preceding chapter of this book. We only mention here the methods which have especially been used for nanocomposite materials as colloidal solutions or thin films Degenerate four-wave mixing (DFWM) and optical phase conjugation, which provide the modulus of x only and may be completed by Interferometry techniques to get its phase as well, optical limiting, optical Kerr shutter, and z-scan, which is probably the most common technique used in recent years due to its ability to provide simultaneously the nonlinear refraction and absorption coefficients of the same sample point [118],... 

Kasai, H., Kanbara, H., lida, R., Okada, S., Matsuda, H., Oikawa, H., and Nakanishi, H., Optical Kerr shutter response of organic microcrystals, Jpn. J. Appl. Phys., 34, L1208, 1995. 

Using powerful polarized light pulses instead of electrical pulses to induce birefringence in traditional Kerr cell liquids, an optical Kerr shutter has been developed with wide ranging applications to picosecond measurements [11.22]. 

The infrared and green pulses are subsequently separated by a dichroic beam splitter. The infrared pulses travel directly to the ultrafast optical kerr effect shutter (24) while the green pulses are diverted through an optical delay line which consists of one movable and two fixed prisms. The shutter consists of a cell of carbon disulfide placed between two crossed polarizers,... 

Microcrystals of some diacetylenes, prepared by the reprecipitation method, have been studied as dispersions in liquid media. Interesting behavior has been observed in the solid-state polymerization of diacetylene monomers and with the optical properties of polydiacetylene (PDA) microcrystals. First, the polymerization perfectly proceeded from one end to the other end of the diacetylene microcrystals. Next, the excitonic absorption peak position was found to shift to higher energy side with decreasing size of the PDA microcrystals. The size effect was observed even for crystals as large as 100 nm or more in contrast to conventional quantum effect of inorganic semiconductors where size effect is observed only for microciystals of less than about 10 nm size. In addition, since the microcrystal dispersions in water have low optical loss, the c tical Kerr shutter response of PDA microciystals could be measured, and the non-resonant value was estimated to be on the order of 10 to 10" esu in very low concentrations (ca. 10 M). 

The Kerr shutter consists of a Kerr cell filled with a liquid, such as nitrobenzene, placed between two crossed polarizers the electric field is arranged to be perpendicular to the axis of the light beam and at 45° to the axis of the polarizers. In the absence of a field there is no optical path through the device. When the field is switched on the nitrobenzene becomes doubly refracting and a path opens between the crossed polarizers. 

There is another way to obtain giant laser pulses of a few ns duration, known as active Q-switching. The shutter is an electro-optical cell which is triggered at some preset time after the pump flash. These electro-optical shutters are Kerr cells or Pockels cells. 

Figure 7. Laser-induced absorbance changes at 561 nm as a function of time in detergent solubilised bovine rhodopsin (X) and isorhodopsin (9) at room temperature. Bathorhodopsin is the only intermediate during the bleaching of bovine rhodopsin known to absorb strongly at 561 nm. The energy of the 530-nm pump pulse was about 10 4J the energy of the 561-nm probe pulse was about 10 7J. The beam sizes were about 1 mm2 for the pump and 0.5 mm2 for the probe. The samples (about 1.5 mL) were held in 0.5-cm cuvettes. The concentrations were about 4 A cm I at the absorption peaks near 500 nm the ratios A Ajjj were about 0.3 and ratios ASsa. As<)o were about 0.7 for rhodopsin and 0.5 for isorhodopsin. Each data point shown is the average of six (rhodopsin) and nine (isorhodopsin) laser shots. Typical mean standard deviations are 0.03. The zero time is located using a 0.5 cm CS2 Kerr optical shutter at the sample site. The half width at half maximum for the CS2 shutter prompt response curve is about 6 ps.

---