Kerr Shutter Research Articles

Operation of a synchronously pumped infrared dye laser.

Ultra-short infrared pulses were generated from a DNP 1040 dye laser synchronously pumped by a CPM glass laser newly constructed. Short (3-4 ps) pulses of about 100 per shot were obtained from the glass laser, in which a saturable absorber (NDL 112) of 0.5 mm in thickness was set in the center of a linear cavity of 1.0 min length and a glass rod (LHG-8.5φ, 75l) was placed between the cell and a coupling mirror. These glass laser pulses pumped synchronously the dye laser, the dye cell of which was contacted with the rear mirror and the cavity length was adjusted to be a half of the pump laser. The pulse width of the infrared dye laser of weak intensi-ty was measured by an optical Kerr shutter method with a CS2 cell and the glass laser. The pulse width of a transmitted signal was 3.0 ps including the responce time of the Kerr shutter and the gate pulse width in convolution. The attainable pulse width of this dye laser is estimated to be ab-out 1.0 ps or less for the Gaussian pulse profile by deconvolution.

Fluorescence lifetime measurement of semiconductor doped glass by using an incoherent light gated optical Kerr shutter

We measured the fluorescence lifetime of a semiconductor doped glass (Toshiba R-63 red color filter) at the liquid nitrogen temperature by using a novel technique of an incoherent light gated optical Kerr shutter. When the peak intensity of nanosecond excitation pulses was increased to more than 1 kW/mm 2, a short lifetime (70 ps) component built up at the high energy side of the exciton band emission besides the already reported component of several hundred picosecond lifetime.

Optical Kerr shutter performance of a solution of organic nonlinear optical material

An optical Kerr shutter with much higher efficiency than the conventional CS/sub 2/ liquid is demonstrated, utilizing a solution of pi -conjugated monomer material. Third-order nonlinear optical susceptibility chi /sup (3)/ of the solution is evaluated by the efficiency of the Kerr shutter operation. The chi /sup (3)/ value of the solution depends on the molecular density, the molecular orientation behavior, and the dielectric constant of the solvent. To utilize these effects most efficiently, 4'-dimethylamino-N-methyl-4-stilbazolium methylsulfate is dissolved in formamide to the saturation concentration. This results in chi /sup (3)/=3.0*10/sup -12/ esu and a Kerr shutter transmission of four times that of CS/sub 2/. >

All-optical gate with picosecond response in semiconductor-doped glasses

Semiconductor-doped glasses are used as an optical Kerr shutter with less than 3ps on/off switching time at 100 MHz repetition rate.

Measurement of dephasing time using incoherent light in the Kerr shutter configuration

We propose a convenient signal-selective method to measure the dephasing time using incoherent light performed in the Kerr shutter configuration. The advantage of this method is easy alignment, which allows one to obtain a better signal-to-noise ratio than with ordinary forward two-beam degenerate four-wave mixing. The dephasing time of Cresyl Violet doped in a polymethyl methacrylate film obtained by this method is compared with the result from ordinary two-beam degenerate four-wave mixing.

Incoherent light gated optical Kerr shutter for fluorescence lifetime measurement

A new method of measuring fluorescence lifetime which is much shorter than the pulse width was developed using an optical Kerr shutter and incoherent light. While a sample was excited by second harmonic light of the output pulse of a Q-switched YAG laser, an optical Kerr shutter was gated with the fundamental light of the same laser pulse. The transmitted intensity of the fluorescence through the Kerr shutter was measured by changing the delay time between the second harmonic and the fundamental light. A resolution time of 30 ps was obtained by using a Q-switched YAG laser pulse of 7 ns duration.

Picosecond fluorimeter using the optical Kerr effect for the direct and automatic recording of a whole time-resolved emission spectrum

Using an optical Kerr shutter and sophisticated automatization procedure, we have shown that it is possible to record routinely, with a good accuracy, and in an experiment consuming a comfortable time, time-resolved emission spectra of short-lived species in the time scale of 10 ps and in the spectral range 3900–9000 Å. This system will allow us to obtain a better understanding of ultrafast dynamics in solution, where time spectral changes provide new insight.

Optical sampling using an all-fiber optical Kerr shutter

An all-fiber optical Kerr shutter consisting of a short single-mode fiber and a highly birefringent fiber which serves not only as a polarizer but also as a wavelength filter to reject pump light is successfully realized. By utilizing the Kerr shutter, optical sampling is demonstrated. Time-varying signal light from a laser diode at λ=0.84 μm is sampled into a train of pulses through the Kerr shutter which is driven by an intense light pulse at λ=1.064 μm. The applications to high-speed signal processing and the generation of picosecond optical pulse are promising because of the fiber’s fast response of optical Kerr effect.

Efficient femtosecond optical Kerr shutter

Conjugated molecules, with large optical nonlinearities, are tested as materials usable for femtosecond optical Kerr shutter technique. With β-carotene, in acetone solution, we have achieved responses limited by the 100-fs width of the optical pulses and characterized by a resolution better than 1 ps with a dynamic range of 100.

Laser pulse selection with krypton triggered Kerr shutter

A 16 kV krypton pulse generator and a 30 kV krypton activated spark gap are developed to operate a Kerr cell shutter. The shutter is used to select single picosecond light pulses from a mode locked laser and to separate nanosecond light signals from a free running laser.

Picosecond luminescence spectroscopy of electron-hole plasmas and excitons in GaAs

The dynamics of optically excited free carriers and excitons are studied by means of picosecond luminescence spectroscopy. A streak camera as well as an optical Kerr shutter are used for detection. The bimolecular recombination coefficient for the spontaneous recombination of the electron hole plasma is determined. The time-resolved emission spectra demonstrate that plasmon interaction extends the emission of the electron hole plasma towards lower energies. Free excitons are screened out in the plasma state, and an gradually increasing number is formed as the free carrier density falls below 5 x 10 16 cm -3.

Time-dependent multiphoton absorption and optical Kerr effect in liquid CS2

Multiphoton absorption processes in liquid CS2 were observed when the power density of 1.05 μm ps laser pulse exceeded 4 GW/cm2. Laser pulse distortion was achieved involving the combination of multiphoton absorption and optical Kerr effect. These effects can affect the overall response kinetics of Kerr shutters for extracting temporal information on chemical systems.

FLUORESCENCE KINETICS OF SPINACH CHLOROPLASTS MEASURED WITH A PICOSECOND OPTICAL KERR GATE

Abstract. An overview of the reported chlorophyll a fluorescence lifetimes from green plant photosystems is presented and the problems encountered in the measurement of fluorescence lifetime using two currently available picosecond techniques are discussed.The fluorescence intensity of spinach chloroplasts exposed to 10 ps flashes was measured as a function of time after the flash and wavelength of observation by the ultrafast Kerr shutter technique. Using a train of 100 pulses separated by 6ns and with an average photon flux per pulse of ˜2 times 1014 photons/cm2, the fluorescence intensity at 685 nm (room temperature) was found to decay with two components, a fast one with a 56 ps lifetime, and a slow one with a 220 ps lifetime. The 730 nm fluorescence intensity at room temperature decays as a single exponential with a 100 ps lifetime. The 730 nm fluorescence lifetime was found to increase by a factor of 6 when the temperature was lowered from room temperature to 90 K while the lifetime of 685 and 695 nm fluorescence were unchanged. At room temperature, the fast and slow components at 685 nm are attributed to the emission from pigment system I (PS I) and PS II, respectively. It is likely that the absolute values of lifetimes, reported here, may increase if single ps low intensity flashes are used for these measurements.

Picosecond light scattering measurements of cataract microstructure

A picosecond range-gated light scattering technique is used to measure the microstructure of cataracts in the living eye, with a resolution of the order of the wavelength of light. The cataract is illuminated with ultrashort pulses of light derived from a mode-locked Nd:glass laser. The pulses backscattered by the opacity are collected at several angles simultaneously by an array of fiber-optic light guides whose outputs are sequentially sampled by a multichannel picosecond Kerr shutter. This shutter transmits only that light which is scattered from the desired depth in the eye, while blocking from the detector any light scattered by foreground or background tissue and reducing multiple scattering effects. The size distribution of scatterers in the cataract is deduced from the angular distribution of scattering intensities by application of Mie theory. The results of experiments with suspensions of latex microspheres and with rabbit cataracts in vivo are presented. Cataract microstructure down to 0.5 microm has been measured in a rabbit eye and verified with electron microscopy.

Gated optical multichannel analyzer for ruby laser scattering from plasma

An optical detection system is described which employs a commercial multichannel analyzer, augmented by a flat spectral response image intensifier and Kerr shutter, to provide time-resolved, sensitive detection of plasmascattered ruby laser light. Operating characteristics are discussed and scattered spectra from CO2 laser induced hydrogen plasma are shown.

Picosecond pulse distortion in optical fibers

Low-loss glass fibers are a prospective transmission medium for optical communication systems. To study their dispersion characteristics, we investigated the propagation of short optical pulses in up to 10 m of cladded fiber. The pulses, 7 ps long and 6 THz in spectral width, were derived from a mode-locked Nd:glass laser by frequency doubling (0.53-μm wavelength). We measured the broadened pulses emerging from the fiber by a sampling technique that employed an optical Kerr shutter of 10 ps gating time. The fiber had a core diameter of 11 μm and an index difference of 1 percent between core and cladding. The loss was about 1.8 dB/m. Our measurements showed satisfactory agreement with a theory that takes material dispersion and mode dispersion into account and assumes strong attenuation of the high-order modes in the particular fiber tested. At the end of 10 m, the 7-ps pulse reached a width of 110 ps, haft of which can be accounted for by material dispersion. When we extrapolate these results to practical systems, we conclude that pulses from a light-emitting diode transmitted through a fiber with the above design would broaden by at least 2.6 ns/km (because of material dispersion), and possibly by as much as 33 ns/km, if all modes were excited and reached the detector with comparable attenuation and negligible coupling.

Photoluminescence of CdSe with picosecond time resolution

The temporal evolution of luminescence of CdSe at He-temperature is studied after picosecond-pulse photo excitation with a Kerr shutter technique capable of 15 psec resolution.

An Apparatus for the Precise Determination of Lifetimes of Atomic States

The time which elapses between excitation of an atom by a pulse of light and subsequent emission of radiation may be measured by a delayed coincidence technique. A system which is suitable for measuring lifetimes of atomic states in the range 10(-7)-10(-8) sec, employing a high speed Kerr shutter in conjunction with a time-to-pulse height converter and kicksorter, is described.