A passively, Q-switched laser is described. The laser may operate at an eye-safe lasing wavelength of 1.34 microns and use a gain element of Nd:YVO.sub.4 and a saturable absorber element of V:YAG with a space separating the gain element and saturable absorber element. The Q-switched laser is pumped by a grating stabilized laser diode. The laser may be used in laser ranging applications.

The disclosure provides a high-frequency-reproducibility laser frequency stabilization method and device based on multi-point acquisition of laser tube temperature. The laser frequency stabilization device includes: a frequency stabilization control circuit. The frequency stabilization control circuit includes a polarizing beam splitter, an optical power conversion circuit, an A/D conversion circuit, a temperature measuring circuit, a microprocessor, a D/A converter and a heating film driver. The polarizing beam splitter is disposed outside any one of laser transmitting holes. The optical power conversion circuit is disposed on reflection and refraction optical paths of the polarizing beam splitter. The optical power conversion circuit, the A/D conversion circuit, the microprocessor, the D/A converter, the heating film driver and a plurality of groups of heating films are sequentially in one-way connection. Temperature sensors, the temperature measuring circuit and the microprocessor are sequentially in one-way connection.

Apparatus for providing optical radiation (15), which apparatus comprises an optical input (13), a coupler (2), a first semiconductor amplifier (3), a controller (4), a preamplifier (61), a power amplifier (62) and an output fibre (5), wherein: the optical input (13) is for receiving input optical radiation (14); the optical input (13) is connected in series to the coupler (2), the first semiconductor amplifier (3), the preamplifier (61), the power amplifier (62), and the output fibre (5); the apparatus being characterized in that: the first semiconductor amplifier (3) comprises a waveguide (6) having a low reflecting facet (8); the first semiconductor amplifier (3) is in a double pass configuration such that the low reflecting facet (8) is connected to both the optical input (13) and the preamplifier (61) via the coupler (2); and the controller (4) is configured to cause the waveguide (6) of the first semiconductor amplifier (3) to operate in saturation thereby enabling the first semiconductor amplifier (3) to reduce non-linear effects in the preamplifier (61), the power amplifier (62), and the output fibre (5).

A femtosecond pulse laser apparatus includes a pump light source configured to provide a pump light, a gain medium configured to obtain a gain of a laser light using the pump light, a first curved mirror and a second curved mirror, which are provided at both sides of the gain medium, an output mirror configured to transmit a portion of the laser light and reflect the other portion of the laser light to the gain medium, a mode locking portion configured to generate a femtosecond pulse of the laser light, and an acoustic wave generator configured to provide an acoustic wave into the gain medium so as to adjust self-phase modulation of the laser light.

A laser apparatus according to an aspect of the present disclosure includes: a master oscillator; at least one amplifier disposed on an optical path of a first pulse laser beam output from the master oscillator; a sensor disposed on an optical path of a second pulse laser beam output from the at least one amplifier; and a laser controller. The laser controller causes the laser apparatus to perform burst oscillation based on a burst signal from an external device, and performs processing of controlling a beam parameter based on a sensor output signal obtained from the sensor in a burst duration, and processing of detecting self-oscillation light from the amplifier based on a sensor output signal obtained from the sensor in a burst stop duration.

A laser apparatus according to an aspect of the present disclosure includes: a master oscillator; at least one amplifier disposed on an optical path of a first pulse laser beam output from the master oscillator; a sensor disposed on an optical path of a second pulse laser beam output from the at least one amplifier; and a laser controller. The laser controller causes the laser apparatus to perform burst oscillation based on a burst signal from an external device, and performs processing of controlling a beam parameter based on a sensor output signal obtained from the sensor in a burst duration, and processing of detecting self-oscillation light from the amplifier based on a sensor output signal obtained from the sensor in a burst stop duration.

A laser apparatus according to the present disclosure includes an excitation light source configured to output excitation light, a laser crystal disposed on an optical path of the excitation light, a first monitor device disposed on an optical path of transmitted excitation light after having transmitted through the laser crystal to monitor the transmitted excitation light, a temperature adjustment device configured to adjust a temperature of the excitation light source to a constant temperature based on a temperature command value, and a controller configured to change the temperature command value based on a result of monitoring by the first monitor device.

Disclosed is a laser system including a first laser and a second laser. The first laser includes a laser cavity, and a gas phase molecular gain medium disposed in the laser cavity, the gain medium having an absorption band. The second laser is a solid state laser configured to be continuously tunable, with respect to an emission wavelength of the second laser, over the absorption band of the gain medium, and the second laser is tuned to pump rotational vibrational transitions in the gain medium to achieve a rotational population inversion.

An exposure method includes reading data representing a relationship between a first parameter relating to an energy ratio between energy of first pulsed laser light having a first wavelength and energy of second pulsed laser light having a second wavelength longer than the first wavelength and a second parameter relating to a sidewall angle of a resist film that is the angle of a sidewall produced when the resist film is exposed to the first pulsed laser light and the second pulsed laser light, and determining a target value of the first parameter based on the data and a target value of the second parameter; and exposing the resist film to the first pulsed laser light and the second pulsed laser light by controlling a narrowed-line gas laser apparatus to output the first pulsed laser light and the second pulsed laser light based on the target value of the first parameter.

An exposure system according to an aspect of the present disclosure includes a laser apparatus emitting a pulse laser beam, an illumination optical system guiding the pulse laser beam to a reticle, a reticle stage moving the reticle, and a processor controlling emission of the pulse laser beam and movement of the reticle. The exposure system performs scanning exposure of a semiconductor substrate by irradiating the reticle with the pulse laser beam. The reticle has first and second regions. The processor instructs the laser apparatus about, based on proximity effect characteristics corresponding to the first and second regions, a value of a control parameter of the pulse laser beam corresponding to each region so that the laser apparatus emits the pulse laser beam with which a difference of the proximity effect characteristic of each region from a reference proximity effect characteristic is in an allowable range.