An external cavity laser apparatus and method wherein wavelength or channel selection is carried independently from adjustment of external cavity optical path length. The apparatus comprises a wavelength or channel selector tuner and an external cavity tuner, wherein the wavelength tuner is uncoupled from the external cavity tuner. The tuning mechanisms for wavelength selection and cavity optical path length are configured to operate independently or orthogonally with respect to each other. The wavelength tuner may operate according to a first, channel selection signal, while the external cavity tuner operates according to a second, external cavity adjustment signal. The wavelength tuner and external cavity tuner may operate under the control of the same, or of separate controllers. The channel selection signal may be derived from a look-up table of adjustment parameter data accessed by a controller, and the external cavity adjustment signal may be derived from an error signal from a detector configured to measure external cavity loss.

External cavity laser apparatus with orthogonal tuning of laser wavelength and cavity optical path length

An error signal generation system and method for continuous and accurate positioning of a tunable element used in association with a coherent light source. A tunable element is positioned in a coherent light beam with a fixed frequency or wavelength, and a detector is positioned in association with the light beam and tunable element that is capable of generating an error signal indicative of spatial losses associated with the positioning of the tunable element in the light beam. A tuning assembly is operatively coupled to the tunable element and detector and is configured to position the tunable element according to the error signal generated by the detector.

Error signal generation system

A new laser perforator has been invented for perforating skin with a perforation to permit blood under a surface of the skin to flow out, the perforator in one embodiment having a laser light source for producing an output laser beam, and a mode distribution apparatus for intercepting the output laser beam to control distribution of laser energy of the output laser beam across the perforation of the skin. A laser perforator is disclosed for perforating skin with a perforation to permit blood under a surface of the skin to flow out, the perforator in one embodiment having a laser light source for producing an output laser beam having an energy level between about 0.1 to about 2.0 Joules, the perforation ranging in diameter between about 0.1 to about 2.0 millimeters, in depth between about 0.5 to about 4.0 millimeters, and ranging in width between about 0.05 to about 0.2 millimeters. A method is also disclosed for perforating skin for blood sampling.

Laser dermal perforator

A wavelength conversion apparatus has an optical amplifier, a wavelength converter, and an optical coupler coupled to form an optical ring resonator. The optical amplifier supplies pump light. The wavelength converter generates converted light, either from the pump light alone or by interaction between the pump light and signal light supplied from a signal source. The optical coupler extracts the converted light. The optical ring resonator preferably includes a tunable optical bandpass filter that defines the wavelength of the pump light. The optical coupler may also couple the signal light into the optical ring resonator, preferably through a polarization beam splitter and at least one polarization rotator, making the apparatus insensitive to the polarization of the signal light.

Wavelength conversion apparatus with improved efficiency, easy adjustability, and polarization insensitivity

Method and apparatus for stabilization of pulse energies produced by a continuously pumped, Q-switched, solid-state or gas laser, through control of the optical power delivered by an optical pump to the laser, in order to limit the energy emitted in any single laser pulse as a result of Q-switching. The laser pump is driven at full strength for a selected initial refresh time t r . If a Q-switch trigger signal is received by the laser before the elapsed time Δt has reached the refresh time t r , the laser emits a pulse with the reduced energy stored in the laser at that time. If the elapsed time reaches or exceeds the refresh time t r , the optical pump power subsequently delivered to the laser is reduced to a lower level, which may be time-dependent, that is sufficient to maintain the net energy stored in the laser at a predetermined value so that the energy in a subsequently emitted laser pulse does not exceed a selected limit. Numerous techniques for controlling the optical pump power delivered are disclosed.

Laser pump control for output power stabilization

There is disclosed an optically pumped solid-state laser with a dielectric crystal or glass host for the active medium. The pulse frequency, phase, height and width of relaxation oscillation pulsing are controlled by externally detecting the phase difference between a stable periodic perturbation of the pump light and the output pulse, then externally feeding back a signal to restore the laser output pulse phase to a fixed relationship to the phase of the perturbation. The perturbation can be provided by a small luminescent diode. Alternatively, the resonator loss can be modulated at the relaxation oscillation frequency by an acoustic cell in which the perturbations are scaled down by two or three orders of magnitude from those in an acoustic Q-switch. Moreover, relaxation oscillation pulsing of a single laser mode and frequency can be stimulated by employing the foregoing control technique and concurrently preventing spatial hole burning, specifically by varying the optical spacing between the ends of the laser rod and respective ones of the resonator mirrors simultaneously in inverse relationship.

Laser with feedback circuit for controlling relaxation oscillation

Single frequency laser oscillation is realized by including within the laser cavity a resonant etalon, tuned to the desired laser frequency. This has the effect of suppressing all other modes while permitting the laser to oscillate at the desired single frequency. In addition, the etalon tuning is frequency modulated about the desired frequency, producing an amplitude modulation of the laser signal. The amplitude modulation thus produced is sensed by a phase detector which generates an error signal whenever the laser frequency tends to deviate from the mean, etalon frequency. The error signal is used, in turn, to retune the laser cavity. It is an advantage of the present arrangement that spurious frequency modulation of the laser frequency, introduced by the stabilization system, is substantially less than that produced by comparable prior art stabilization circuits. Furthermore, such modulation can be conveniently reduced, or eliminated, by the addition of a dummy etalon driven in antiphase to the active etalon.

Frequency stabilized laser

There is disclosed an optically pumped laser employing a pump cavity including two facing internally reflective conical elements within which an elongated laser element and an elongated pump lamp are respectively axially oriented. Typically, an internally-reflective cylindrical element connects the two conical elements. As compared to prior pump cavities, this cavity provides superior fundamental transverse mode operation and simplified fabrication.

Laser pump cavity with conical geometry

There is disclosed a coherent optical oscillator in which evanescent wave coupling between two surfaces, at least one of which is curved, provides beam shaping and improved overall conversion efficiency. In general, bicylindrical curvature is provided, for example, by appropriately oriented cylindrical curvatures of the two surfaces. There are specifically disclosed a second-harmonic generator having improved conversion efficiency and a thin-film laser having improved output characteristics.

Hans Guenter Danielmeyer

Papers

Laser with feedback circuit for controlling relaxation oscillation

Frequency stabilized laser

Laser pump cavity with conical geometry

Evanescent wave coupling technique for beam shaping