We present a cw chromium-doped forsterite laser that permits rapid wavelength tuning over a broad bandwidth and demonstrate the application of this source to frequency-domain ranging and optical tomography. The entire tuning range of 1200 to 1275 nm can be swept in less than 500 micros . This permits frequency-domain ranging to be performed with a scan rate of 2 kHz and an axial resolution of 15 microm .
The development of techniques for high-speed image acquisition in optical coherence tomography (OCT) systems is essential for suppressing motion artifacts when one is imaging living systems. We describe a new OCT system for performing micrometer-scale, cross-sectional optical imaging at four images/s. To achieve OCT image-acquisition times of less than 1 s, we use a piezoelectric fiber stretcher to vary the reference arm delay. A Kerr-lens mode-locked chromium-doped forsterite laser is employed as the low-coherence source for the highspeed OCT system. Dynamic, motion-artifact-free in vivo imaging of a beating Xenopus laevis (African frog) heart is demonstrated.
An all-solid-state Kerr-lens mode-locked Cr:forsterite laser operating at 1.28 microm is demonstrated as a shortcoherence-length, high-average-power source for optical coherence tomographic (OCT) imaging. We achieve ultrahigh resolution by spectrally broadening the laser pulses, using self-phase modulation in a dispersionshifted single-mode fiber. OCT imaging with a resolution of 6 microm and a dynamic range of 115 dB is achieved.
We report the implementation and operation of novel superhigh-reflectivity negative-dispersion dielectric mirrors for use in tunable ultrafast laser systems. The mirror structure is divided into two distinct regions: an underlying superhigh-reflectivity dielectric quarter-wavelength stack and an overlying negative-dispersion section consisting of only a few layers and forming simple multiple Gires-Tournois interferometers. The example that we present was designed for operation from 800 to 900 nm and has a near-constant group-delay dispersion of -40 fs(2) and a peak reflectivity greater than 99.99%. We show a comparison of the predicted and the measured mirror performance and application of these mirrors in a mode-locked Ti:sapphire laser tunable from 805 to 915 nm.
An investigation of spectral hole burning effects is reported in the gain region of InGaAs/AlGaAs strained-layer single quantum well diode lasers, using a heterodyne nondegenerate pump-probe technique. This technique permits simultaneous measurement of the femtosecond dynamics and spectral dependence of transient gain in semiconductor lasers. At high bias current, strong spectral hole burning effects were observed.
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