A passively, Q-switched laser operating at an eye safe wavelength of between 1.2 and 1.4 microns is described. The laser may operate at a lasing wavelength of 1.34 microns and use a gain element of Nd:YVO.sub.4 and a saturable absorber element of V:YAG. The systems and methods to produce short pulses having a pulse duration less than 1 ns and high energy pulses having pulse energies greater than 2 μJ are described.

Coupled-cavity vertical cavity surface emitting lasers (VCSELs) are provided by the present disclosure. The coupled-cavity VCSEL can comprise a VCSEL having a first mirror, a gain medium disposed above the first mirror, and a second mirror disposed above the gain medium, wherein a first cavity is formed by the first mirror and the second mirror. A second cavity is optically coupled to the VCSEL and configured to reflect light emitted from the VCSEL back into the first cavity of the VCSEL. In some embodiments, the second cavity can be an external cavity optically coupled to the VCSEL through a coupling component. In some embodiments, the second cavity can be integrated with the VCSEL to form a monolithic coupled-cavity VCSEL. A feedback circuit can control operation of the coupled-cavity VCSEL so the output comprises a target high frequency signal.

A method includes driving, while producing a burst of pulses at a pulse repetition rate, a spectral feature adjuster among a set of discrete states at a frequency correlated with the pulse repetition rate; and in between the production of the bursts of pulses (while no pulses are being produced), driving the spectral feature adjuster according to a driving signal defined by a set of parameters. Each discrete state corresponds to a discrete value of a spectral feature. The method includes ensuring that the spectral feature adjuster is in one of the discrete states that corresponds to a discrete value of the spectral feature of the amplified light beam when a pulse in the next burst is produced by adjusting one or more of: an instruction to the lithography exposure apparatus, the driving signal to the spectral feature adjuster, and/or the instruction to the optical source.

A method includes driving, while producing a burst of pulses at a pulse repetition rate, a spectral feature adjuster among a set of discrete states at a frequency correlated with the pulse repetition rate; and in between the production of the bursts of pulses (while no pulses are being produced), driving the spectral feature adjuster according to a driving signal defined by a set of parameters. Each discrete state corresponds to a discrete value of a spectral feature. The method includes ensuring that the spectral feature adjuster is in one of the discrete states that corresponds to a discrete value of the spectral feature of the amplified light beam when a pulse in the next burst is produced by adjusting one or more of: an instruction to the lithography exposure apparatus, the driving signal to the spectral feature adjuster, and/or the instruction to the optical source.

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.

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 wavelength control method of a laser apparatus includes sequentially obtaining target wavelength data of a pulse laser beam, sequentially saving the target wavelength data, sequentially measuring a wavelength of the pulse laser beam to obtain a measured wavelength, calculating a wavelength deviation using the measured wavelength and the target wavelength data at a time before a time when the measured wavelength is obtained, and feedback-controlling the wavelength of the pulse laser beam using the wavelength deviation.

A gas laser apparatus includes an enclosure, a window holder, a window, and a sealing member. The window holder further having an extending surface located on the side toward which reflected light travels, the reflected light being reflected off the window, the extending surface being continuous with the end surface and extending in a direction away from the window, the extending surface irradiated with the reflected light. A line is obtained by symmetrically folding back the optical axis of the reflected light at the position, on the extending surface, that is irradiated with the reflected light with respect to a reference line passing through the irradiated position and perpendicular to the extending surface. The line 602 extends across a normal to the window in the direction from the extending surface toward the window from the side facing the outer circumference of the window toward the center axis of the window.

The present disclosure provides an ultrafast laser that outputs multiple wavelengths. The ultrafast laser includes a fundamental frequency ultrafast laser unit, an optical beam splitting and polarization controlling unit, a multiple frequency unit, and an optical beam combining unit. The fundamental frequency ultrafast laser generates a multiple frequency ultrafast laser by the multiple frequency unit, such as double frequency light, triple frequency light, etc., and the optical beam combining unit makes the fundamental frequency light and the double frequency light output in a light outlet, the controlling unit controls the wavelength of the laser of the light outlet by controlling the polarization state of the laser. The ultrafast laser of the present disclosure can realize fast switching output among the fundamental frequency light and multiple frequency light, and output of combined pulse fundamental frequency light and double frequency light. The present disclosure also provides a strong powerful laser tool.

The present disclosure provides an ultrafast laser that outputs multiple wavelengths. The ultrafast laser includes a fundamental frequency ultrafast laser unit, an optical beam splitting and polarization controlling unit, a multiple frequency unit, and an optical beam combining unit. The fundamental frequency ultrafast laser generates a multiple frequency ultrafast laser by the multiple frequency unit, such as double frequency light, triple frequency light, etc., and the optical beam combining unit makes the fundamental frequency light and the double frequency light output in a light outlet, the controlling unit controls the wavelength of the laser of the light outlet by controlling the polarization state of the laser. The ultrafast laser of the present disclosure can realize fast switching output among the fundamental frequency light and multiple frequency light, and output of combined pulse fundamental frequency light and double frequency light. The present disclosure also provides a strong powerful laser tool.