A hybrid optical amplifier is proposed that includes a preamplifier element formed of single-clad Ho-doped optical fiber and a power amplifier element formed of single-clad Tm-doped (or Tm—Ho co-doped) optical fiber. The preamplifier is used to impart gain to an input signal propagating at a wavelength λ.sub.S in the presence of a first pump beam operating at λ.sub.P1, creating an amplified output over a defined transmission bandwidth. The power amplifier element is disposed at the output of the preamplifier element and provides an additional level of gain to the output of the preamplifier element in the presence of a second pump beam operating at λ.sub.P2. A passband filter may be used between the preamplifier and the power amplifier to ensure that only wavelength components within the defined transmission bandwidth are applied as an output to the power amplifier.

A tunable narrow-linewidth photo-generated microwave source based on polarization control includes a high-reflectivity fiber grating, a high-gain fiber, a low-reflectivity polarization-maintaining fiber grating, a stress adjusting device, a single-mode semiconductor pump laser, an optical wavelength division multiplexer, a polarization beam splitter, a polarization controller, an optical coupler, and a photoelectric detector. Birefringence distribution in the low-reflectivity polarization-maintaining fiber grating is controlled by adjusting a stress magnitude of the stress adjusting device to the low-reflectivity polarization fiber grating, thereby controlling a laser frequency working in different polarization modes in a resonant cavity, and a tunable narrow-linewidth photo-generated microwave source is generated by a beat-frequency technology using a dual-wavelength narrow-linewidth laser with variable frequency intervals.

A passively mode-coupled fiber oscillator includes a bidirectional loop, a unidirectional loop, and a 3×3 coupler. The bidirectional loop and the unidirectional loop are coupled to each other by the 3×3 coupler. The bidirectional loop includes a first amplifying fiber. The fiber oscillator has overall a normal dispersion.

Example ultra narrow linewidth Brillouin lasers are disclosed that are pumped by pump lasers that are controlled via optimal control schemes in order to stabilize the Brillouin laser output frequency and minimize the Brillouin output linewidth. The control schemes are based on feedback loops to match the pump laser frequency to the optimum Stokes shift on the one hand and to line-narrow the pump laser linewidth on the other hand via comparing the linewidth of the pump laser with the linewidth of the Brillouin laser. The feedback loops in the control schemes can be partially or fully replaced with feedforward control schemes, allowing for larger bandwidth control. Provision for simultaneous oscillation of the Brillouin lasers on two polarization modes allows for further line-narrowing of the Brillouin output. The ultra-narrow linewidth Brillouin lasers can be advantageously implemented as pumps for microresonator based frequency combs, and can also be integrated to the chip scale and be constructed with minimal vibration sensitivity. The ultra-narrow linewidth Brillouin lasers can be widely tuned and a frequency readout can be provided via the use of a frequency comb. When phase locking a frequency comb to the Brillouin laser, ultra-stable microwave generation can be facilitated.

A pulse configurable laser unit is an environmentally stable, mechanically robust, and maintenance-free ultrafast laser source for low-energy industrial, medical and analytical applications. The key features of the laser unit are a reliable, self-starting fiber oscillator and an integrated programmable pulse shaper. The combination of these components allows taking full advantage of the laser's broad bandwidth ultrashort pulse duration and arbitrary waveform generation via spectral phase manipulation. The source can routinely deliver near-TL, sub-60 fs pulses with megawatt-level peak power. The output pulse dispersion can be tuned to pre-compensate phase distortions down the line as well as to optimize the pulse profile for a specific application.

A passive mode-coupled fiber oscillator includes a bidirectional loop, a unidirectional loop, and a 3x3 coupler. The bidirectional loop and the unidirectional loop are coupled to one another via the 3x3 coupler. The bidirectional loop includes a first amplification fiber that is doped using at least one element selected from the group consisting of ytterbium, neodymium, erbium, thulium, and holmium. The fiber oscillator further includes a dispersion compensation element. The fiber oscillator has an anomalous dispersion overall.

An optical device includes first and second 45° Faraday rotators. A 45° polarizer is located between the first and second Faraday rotators such that light in a prescribed polarization state that is incident on the first 45° Faraday rotator traverses the first 45° Faraday rotator as well as the 45° polarizer and the second 45° Faraday rotator. In one implementation the optical device is operable to receive a light beam traveling in a first direction and output a light beam that is in a predetermined polarization state. Likewise, the optical device is operable to receive an unpolarized light beam traveling in a second direction opposite the first direction and outputs a light beam that is in a predetermined polarization state. The polarization state in which the two output beams are arranged may be the same or orthogonal to one another.

Apparatus and methods for producing ultrashort optical pulses are described. A high-power, solid-state, passively mode-locked laser can be manufactured in a compact module that can be incorporated into a portable instrument for biological or chemical analyses. The pulsed laser may produce sub-100-ps optical pulses at a repetition rate commensurate with electronic data-acquisition rates. The optical pulses may excite samples in reaction chambers of the instrument, and be used to generate a reference clock for operating signal-acquisition and signal-processing electronics of the instrument.

The ultra-short pulse chirped pulse amplification (CPA) laser system and method of operating CPA laser system include outputting nearly transform limited (TL) pulses by a mode locked laser. The system and method further include temporarily stretching the TL pulses by a first Bragg grating providing thus each stretched pulse with a chirp which is further compensated for in a second Bragg grating operating as as a compressor. The laser system and method further include a pulse shaping unit measuring a spectral phase across the recompressed pulse and further adjusting the deviation of the measured spectral phase from that of the TL pulse by generating a corrective signal. The corrective signal is applied to the array of actuators coupled to respective segments of one of the BGs which are selectively actuated to induce the desired phase change, with the one BG thus operating as both stretcher/compressor and pulse shaper.

In accordance with some embodiments, a light detection and ranging (LiDAR) system comprise: a control system housing; a first LiDAR head housing separate and distinct from the control system housing; a light source within the control system housing configured to produce a first pulse signal; a light detector within the control system housing configured to detect a first return pulse signal associated with the pulse signal; a first pulse steering system within the first LiDAR housing configured to direct the first pulse signal in a first direction; a first fiber coupled to the light source and the first pulse steering system, the first fiber configured to carry the first pulse signal from the light source to the first pulse steering system; and a second fiber configured to carry a first returned pulse signal from the first LiDAR head housing to the light detector.