Ming Lai

Femtosecond ring dye laser: a potential new laser gyro.

Measurements on a passively mode-locked dye laser demonstrate a sensitive gyro-type response, when Fresnel drag in air is used to simulate rotation. Such a response is unexpected for a homogeneously broadened ring laser.

Complete diagnostics of ultrashort pulses without nonlinear process

The present invention provides an arrangement for analyzing or reconstructing incoming pulses of electromagnetic energy in which there is detected (a) the spectral amplitude of at least one pulse and (b) the phase shifts of portions of the pulse with respect to a non-phase shifted portion, and applying an inverse Fourier transform to the detected energy thereby producing the temporal profile of the pulse.

Nonreciprocal measurements in femtosecond ring lasers

Sensitive gyroscopic response has been demonstrated with a passively mode-locked ring dye laser. Rapid change in the phase of scattering has been identified as an important mechanism responsible for the extremely low lock-in threshold of this laser gyro. Coupling between counterpropagating pulses has been confirmed to take place only in the overlapping region of the pulses. Intracavity measurements of the electro-optical effect are demonstrated with fields as small as 20 mV/cm.

Wave–particle duality of a photon in emission

The wave–particle duality of a photon in emission is demonstrated by measuring the interference between spontaneous emissions in nearly opposite directions from a thin layer of organic dye. The interference is the product of a single photon from a single-emission process. It is shown that the Heisenberg uncertainty relation requires that the interference generated by the spontaneously emitted photon and the recoil transferred to the molecule by the emission cannot be observed simultaneously.

Transversely pumped 11-pass amplifier for femtosecond optical pulses

An off-axis near-concentric interferometer is used for multiple passages through a small (2-mm-diameter) cylindrical volume of amplifying dye. The gain volume is pumped transversely by a copper-vapor laser, in a geometry designed for uniform pump. Pulse-to-pulse reproducibility better than 1% is obtained by operating with full saturation and using a solvent with a vanishing temperature-induced change in index of refraction (dn/dT = 0).

Interference between spontaneous emission in different directions

Is there coherence between the two beams spontaneously emitted in opposite directions by a thin plane of radiating atoms? A simple interference experiment gives a positive answer to this question.

Energy limiting at a saturable nonlinear interface

Abstract An energy limiter based on nonlinear reflection at an interface between a saturable absorber and a dielectric is demonstrated. Analysis of the experimental data show a very large negative Kerr effect for one of the dyes.

Thermal nonlinear effects in exotic media : application to the study of nonlinear interfaces

Nonlinearities reported as self-focusing in exotic media such as green Chinese tea are identified as thermal selfdefocusing. These large index changes can be used to study hysteresis, power-induced self-switching and cross-switching, the power-induced lensing effect, and other nonlinearities at interfaces.

Ultrafast Detection Of Weak Signals

Femtosecond nonlinear detection techniques for weak signals are discussed. New methods for the characterization of femtosecond signals, in amplitude and phase, are presented.

Spontaneous emission noise reduction of a laser output by extracavity destructive interference

Our recent experiment shows that the oppositely directed spontaneous emission from a thin layer of a fluorescence source is highly coherent. It is proposed that a thin layer of gain medium be applied to a ring cavity and be located at the symmetric point from the output coupler so that the spontaneous emission in the laser outputs are correlated and can be removed from a laser beam by destructive interference technique. A theoretical analysis and a physical interpretation for such a spontaneous emission free laser beam are presented. The potential of using the device as an active laser gyro is discussed.