Techniques for extending distributed acoustic sensing (DAS) range in undersea optical cables are provided. For example, DAS range can be extended by transmitting and amplifying a DAS signal along multiple spans of a first optical fiber, routing or bypassing the DAS signal from the first optical fiber to a second optical fiber different from the first fiber via a high-loss loopback architecture, and returning and amplifying the DAS signal along the same multiple spans back to a DAS device. The DAS device may then receive and process the DAS signal to detect any changes in the DAS environment. The loopback configuration may be based on different types of loopback architecture.

A gas laser device includes a shielding plate that is a first shielding member, and a shielding plate that is a second shielding member. The first shielding member includes a first opening, and a second opening. A laser beam that is to be propagated to discharge regions passes through the first opening. The laser beam that has taken a round trip through the discharge regions after passing through the first opening passes through the second opening. The second shielding plate faces the first shielding member the discharge regions located therebetween. The shielding plate includes an opening that is a third opening. The laser beam that has been propagated through the first opening and the discharge regions, and the laser beam that is to be propagated to the second opening through the discharge regions pass through the third opening. A plane shape of the third opening includes a rectilinear segment.

Disclosed are ideas to produce an add-on device which turns widely used high repetition rate lasers used for 2-photon microscopy into a light source which can be used for 3-photon microscopy. The add-on encompasses a device to reduce the pulse repetition rate of the high repetition rate (>50 MHz) laser source (laser or OPO) to less than 10 MHz which allows for higher pulse energies while maintaining reasonable average powers. If the high repetition sources operate below 1250 nm the add-on shifts or broadens the seed light to cover 1.3 μm to 1.8 μm before amplification. If the high repetition rate source operates at or around 1.3 μm the add-on only needs to amplify the pulse after downshifting the repetition rate. In another implementation the add-on shifts or broadens the 1.3 μm light to cover the spectral range out to 1.8 μm before amplification.

In a laser system according to an aspect of the present disclosure, the following components are disposed: a first container that accommodates a first heater and a first crystal holder holding a first nonlinear crystal and includes a first light incident window via which laser light is incident and a first light exit window via which the laser light exits; a second container that accommodates a second heater and a second crystal holder holding a second nonlinear crystal and includes a second light incident window via which the laser light is incident and a second light exit window via which the laser light exits; and a stage that holds the first and second containers. A controller controls the stage to move the first nonlinear crystal away from the optical path of the laser light and inserts the second nonlinear crystal into the optical path of the laser light.

An apparatus includes at least one Raman medium configured to receive a pump beam and shift at least a portion of the pump beam into a Stokes-shifted output beam. The apparatus also includes a first lens configured to receive and focus the pump beam into the at least one Raman medium. The apparatus further includes first and second retro-lens assemblies, each including at least one prism configured to reflect beams from the at least one Raman medium back into the at least one Raman medium and multiple second lenses configured to control optical propagation of the beams entering and exiting the at least one Raman medium. Multiple pairs of lenses form multiple confocal arrangements of lenses. The pairs of lenses include the first lens and the second lenses of the retro-lens assemblies. The at least one Raman medium is optically positioned between the lenses in the confocal arrangements of lenses.

The present description relates, according to one aspect, to a high-peak-power laser pulse generation system (10), comprising at least one first light source (101) for emitting first laser pulses (I.sub.L), a fiber device (110) for transporting said first laser pulses, comprising at least one first multimode fiber with a single core designed to receive said first laser pulses, and a module (102) for temporally shaping said first laser pulses, arranged upstream of the fiber device, configured so as to reduce the power spectral density of said pulses by reducing the temporal coherence.

A system includes a laser source operable to provide a laser beam, a laser amplifier having a gain medium operable to provide energy to the laser beam when the laser beam passes through the laser amplifier, and a residual gain monitor operable to provide a probe beam and operable to derive a residual gain of the laser amplifier from the probe beam when the probe beam passes through the laser amplifier while being offset from the laser beam in time or in path.

A fluid-cooled laser amplifier module (100) is disclosed which comprises: a casing; a plurality of slabs (110) of optical gain medium oriented in parallel in the casing for cooling by a fluid stream (154, 156); a polarisation rotator (120) disposed between a first group of one or more slabs (111) of the optical gain medium and a second group of one or more slabs (112) of the optical gain medium; optical windows (150, 152) for receiving an input beam or pulse (130) for amplifying by the slabs and for outputting the amplified beam or pulse (140); and fluid stream ports (155, 157) for receiving and discharging the fluid stream for cooling the slabs.

A solid state laser apparatus includes a plurality of cold heads, a cooling apparatus, laser media and a seed light source. The cooling apparatus is configured to cool the plurality of cold heads. The laser media are arranged in contact with each of the plurality of cold heads, and configured to amplify a first laser beam and reflect the first laser beam. The seed light source is configured to irradiate a first laser medium of the laser media with the first laser beam. The first laser medium is arranged on a first of the cold heads. The laser media are configured to reflect the first laser beam irradiated to the first laser medium to a second laser medium of the laser media. The second laser medium is arranged on a second of the cold heads. The cold heads are configured to cool the laser media.

An optical arrangement for pulse compression of a pulsed laser beam includes a grating arrangement comprising at least one diffraction grating, and a beam-expanding device comprising at least one beam-expanding optical element for forming a divergent pulsed laser beam that enters the grating arrangement divergently.