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.

Provided are a monitoring device, a monitoring method, an optical amplifier, and an optical transmission system that are adapted for an increase in the number of cores in a multi-core optical fiber transmission path, and that are suitable for crosstalk monitoring. The monitoring device monitors a multi-core optical fiber transmission path comprising a plurality of use core and at least one or more non-use cores. The monitoring device comprises: an applying means for applying dithering to signal light propagating in the use cores; a monitoring means for monitoring the power of the non-use cores; and a separating means for separating a monitoring result from the monitoring means into power components from the plurality of use cores.

A fractional handpiece and systems thereof for skin treatment include a passively Q-switched laser assembly operatively connected to a pump laser source to receive a pump laser beam having a first wavelength and a beam splitting assembly operable to split a solid beam emitted by the passively Q-switched laser assembly and form an array of micro-beams across a segment of skin. The passively Q-switched laser assembly generates a high power sub-nanosecond pulsed laser beam having a second wavelength.

Disclosed are dielectric cavity arrays with cavities formed by pairs of dielectric tips, wherein the cavities have low mode volume (e.g., 7*10.sup.−5λ.sup.3, where X is the resonance wavelength of the cavity array), and large quality factor Q (e.g., 10.sup.6 or more). Applications for such dielectric cavity arrays include, but are not limited to, Raman spectroscopy, second harmonic generation, optical signal detection, microwave-to-optical transduction, and as light emitting devices.

A semiconductor laser diode is disclosed. In an embodiment a semiconductor laser diode includes a first resonator and a second resonator, the first and second resonators having parallel resonator directions along a longitudinal direction and being monolithically integrated into the semiconductor laser diode, wherein the first resonator includes at least a part of a semiconductor layer sequence having an active layer and an active region configured to be electrically pumped to generate a first light, wherein the longitudinal direction is parallel to a main extension plane of the active layer, and wherein the second resonator has an active region with a laser-active material configured to be optically pumped by at least a part of the first light to produce a second light which is partially emitted outwards from the second resonator.

An optical semiconductor device outputting a predetermined wavelength of laser light includes a quantum well active layer positioned between a p-type cladding layer and an n-type cladding layer in thickness direction. The optical semiconductor device includes a separate confinement heterostructure layer positioned between the quantum well active layer and the n-type cladding layer. The optical semiconductor device further includes an electric-field-distribution-control layer positioned between the separate confinement heterostructure layer and the n-type cladding layer and configured by at least two semiconductor layers having band gap energy greater than band gap energy of a barrier layer constituting the quantum well active layer. The quantum well active layer is doped with 0.3 to 1×10.sup.18/cm.sup.3 of n-type impurity.

An optical fiber connector includes: amplifying fibers in which an active element activated by excitation light is added to a core of each of the amplifying fibers. The amplifying fibers are connected together such that an absorption amount of excitation light per unit length increases with an increase of a distance from an incident end of the excitation light. A mode field diameter of laser light propagating through the core is same among the amplifying fibers.

An optical fiber configured to improve the pump conversion efficiency of an L-band fiber amplifier which uses the multimode pump source. By directly absorbing multimode light including 915 nm, an active fiber core region co-doped with both erbium and ytterbium can provide gain to the L-band signals via stimulated emission. The unwanted C-band amplified spontaneous emission (ASE) light generate from this active fiber core region can be absorbed by another active fiber core region doped with erbium, then provides additional gain to the L-band signals. Active regions and cladding can be configured to match a given spatial mode of the optical signal. Signal-pump combiners with end-coupling or side coupling can be used.

An apparatus may include a diode-pumped solid-state laser oscillator configured to output a pulsed laser beam, a modulator configured to modify an energy and a temporal profile of the pulsed laser beam, and an amplifier configured to amplify an energy of the pulse laser beam. A modified and amplified beam to laser peen a target part may have an energy of about 5J to about 10 J, an average power (defined as energy (J) x frequency (Hz)) of from about 25 W to about 200 W, with a flattop beam uniformity of less than about 0.2. The diode-pumped solid-state oscillator may be configured to output a beam having both a single longitudinal mode and a single transverse mode, and to produce and output beams at a frequency of about 20 Hz.

A highly efficient laser ignition device is provided. The highly efficient laser ignition device fundamentally includes: a pumping light source adopting a multi-chip single emitter-packaged optical fiber output laser diode; a laser medium to which ytterbium is added; and a saturated absorber as a passive Q-switch medium, wherein a pulse of 100-999 ps as the passive Q-switch laser output can be obtained. According to the disclosed, the problems of high cost/low efficiency/low reliance/non-uniformity, which are disadvantages for replacing an ignition device using an electric spark with a laser ignition device, can be solved.