A single-frequency laser apparatus comprises a mirror and a volume Bragg grating (VBG) reflector defining a laser cavity therebetween and an optical gain material for emitting and amplifying an intra-cavity beam in the laser cavity. The optical gain material comprises a transition-metal doped crystal such as a crystal doped with transition-metal ions selected from one or more of Ti.sup.3+ ions, Cr.sup.2+ ions, Cr.sup.3+ ions or Cr.sup.4+ ions. A reflectivity spectrum of the VBG reflector and an optical length of the laser cavity are selected so that a beam output from the laser cavity is a single-frequency output beam and/or includes only one longitudinal mode of the laser cavity. The laser apparatus may provide a robust, compact, low cost, high-power wavelength adjustable (from approximately 650 to 950 nm), narrow linewidth (<100 kHz), single frequency laser source which is suitable for a wide range of applications from laser sensing, spectroscopy, and high precision frequency metrology sectors.

A system for generating extreme ultraviolet light, in which a target material inside a chamber is irradiated with a laser beam to be turned into plasma, includes a first laser apparatus configured to output a first laser beam, a second laser apparatus configured to output a pedestal and a second laser beam, and a controller connected to the first and second laser apparatuses and configured to cause the first laser beam to be outputted first, the pedestal to be outputted after the first laser beam, and the second laser beam having higher energy than the pedestal to be outputted after the pedestal.

There is provided a laser apparatus for a printed electronic system according to an exemplary embodiment of the present invention including: a laser generating unit which oscillates a laser beam; a laser changing unit which changes an intensity or a wavelength of the laser beam oscillated from the laser generating unit; a laser control unit which controls the intensity or a magnitude of the wavelength of the laser beam which is changed by the laser changing unit; and a laser steering unit which changes a traveling direction of the laser beam output from the laser changing unit to be directed to a target, and the laser control unit controls the intensity or the magnitude of the wavelength of the laser beam in accordance with a state of a printing pattern formed on the target.

There is provided a laser apparatus for a printed electronic system according to an exemplary embodiment of the present invention including: a laser generating unit which oscillates a laser beam; a laser changing unit which changes an intensity or a wavelength of the laser beam oscillated from the laser generating unit; a laser control unit which controls the intensity or a magnitude of the wavelength of the laser beam which is changed by the laser changing unit; and a laser steering unit which changes a traveling direction of the laser beam output from the laser changing unit to be directed to a target, and the laser control unit controls the intensity or the magnitude of the wavelength of the laser beam in accordance with a state of a printing pattern formed on the target.

The invention provides an excimer laser system including a means for calibrating laser output to compensate for increased variation in laser optical fibers.

There is provided a laser controller comprising: an electromagnetic radiation source operable to transmit radiation into the environment; a backscatter detector operable to detect backscattered radiation from the environment; and a processor operable to generate a laser control signal based on characteristics of the detected backscattered radiation.

Provided are a time and frequency control method and system for optical comb. The method includes: controlling an optical comb measuring system to start and to generate an optical comb; obtaining monitoring data, wherein the monitoring data comprises a working temperature, a mode-locked frequency and a light pump power, wherein the mode-locked frequency comprises a repetition frequency and a carrier envelope phase locked at the end of starting the optical comb measuring system; determining whether an offset of the mode-locked frequency exceeds a self-feedback adjustment range of a hardware adjustment circuit; and in response to any of the repetition frequency and the carrier envelope phase exceeds the self-feedback adjustment range, adjusting the working temperature and the light pump power until the mode-locked frequency returns back into the self-feedback adjustment range.

An integrated optical linewidth reduction system based on optical feedback and a low-speed electronic control loop to control the optical feedback. Light is tapped and reflected back to the laser with an amplitude, phase or both amplitude and phase adjustment such that the linewidth of the laser is lower than the free-running laser linewidth. The amplitude of the feedback signal may be controlled using an optical attenuator. The phase of the feedback signal may be controlled using a phase shifter. The amplitude of the optical feedback may be monitored by means of a filter and a photodetector, or just a photodetector. The amplitude and/or phase of the optical feedback is monitored by means of a frequency/phase noise discriminator. The phase shifter can be an endless phase shifter

A high-precision repetition rate locking apparatus for an ultra-fast laser pulse includes: an electronic controlling component comprising: a standard clock, configured to provide a high-precision frequency standard; a pulse generator (PG), configured to provide an electrical pulse signal with adjustable repetition rate, pulse width and voltage magnitude; and a signal generator (SG), connected to the standard clock and the PG, and configured to provide a stable frequency signal for the PG, a phase-shift adjusting component, connected to the electronic controlling component and configured to implement phase modulation through electrically induced refractive index change; a resonant cavity component, comprising a phase shifter, a doped fiber, a laser diode, a wavelength division multiplexer and a reflector, and configured to generate a mode-locked pulse; and a detection system, configured to measure a repetition rate of an output pulse.

A high-precision repetition rate locking apparatus for an ultra-fast laser pulse includes: an electronic controlling component comprising: a standard clock, configured to provide a high-precision frequency standard; a pulse generator (PG), configured to provide an electrical pulse signal with adjustable repetition rate, pulse width and voltage magnitude; and a signal generator (SG), connected to the standard clock and the PG, and configured to provide a stable frequency signal for the PG, a phase-shift adjusting component, connected to the electronic controlling component and configured to implement phase modulation through electrically induced refractive index change; a resonant cavity component, comprising a phase shifter, a doped fiber, a laser diode, a wavelength division multiplexer and a reflector, and configured to generate a mode-locked pulse; and a detection system, configured to measure a repetition rate of an output pulse.