# US 12,009,628 B2 · Structure and configuration of the passively Q-switched diode end-pumped solid-state laser

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- Number: US 12,009,628 B2
- Document ID: US12009628B2
- Status: Granted
- Kind: B2
- Application number: 17/560,358
- Filed: 2021-12-23
- Published: 2022-06-30
- Granted: 2024-06-11
- Earliest claimed: 2020-12-24
- Assignees: Viettel Group
- Applicants: Viettel Group
- Inventors: Van Tuan Vu; Trung Anh Hoang; Trung Hieu Le
- Web page: https://patentgrep.com/patent/US12009628B2

## CPC

- H01S 3/1115: using intracavity saturable absorbers
- H01S 3/025: {of solid state lasers, e.g. housings or mountings}
- H01S 3/094049: {Guiding of the pump light}
- H01S 3/094076: {Pulsed or modulated pumping (H01S3/1024 takes precedence)}
- H01S 3/09415: {the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping}
- H01S 3/113: using intracavity saturable absorbers
- H01S 3/1608: {erbium}
- H01S 3/1618: {ytterbium}
- H01S 3/17: amorphous, e.g. glass
- H01S 5/02253: using lenses
- H01S 3/061: {with elliptical or circular cross-section and elongated shape, e.g. rod}
- H01S 3/175: {phosphate glass}
- H01S 5/02208: characterised by the shape of the housings
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL

## Abstract

The passively q-switched diode end-pumped solid-state laser is used the gain medium made of Er:Yb doped crystal and the Q-switch made of Co2+:MgAl2O4 crystal. The optical elements are optimally designed for the resonator to achieve pulse energy in a range 0.5 mJ≤E≤2 mJ with the pulse width in a range of 4 ns-15 ns. The resonator is appropriate to use in laser rangefinders, target designator, and other products in military and civilian applications.

## Claims

### Claim 1

A configuration of a passively q-switched diode end-pumped solid-state laser, comprising:
a laser base attaching optical elements along an optical axis of a diode laser source to form a laser transmitter;
the diode laser source is a pulsed laser source configured to generate a pump laser beam with a center wavelength in a range of 900 nm-1000 nm, which can generate pulsed laser with a peak power in a range of 20 W-120 W, a pulse width in a range of 2 ms-5 ms, and a pulse repetition frequency in a range of 1 Hz-10 Hz;
coupling lenses which are responsible for guiding the pump laser beam from the diode laser source into a gain medium in a resonator cavity, positions of the coupling lenses are varied axially to control a diameter, DB, or cross-section dimensions, a, b, of the pump laser beam entering the gain medium in a range of 0.5 mm-1 mm;
the resonator cavity comprising, an input coupler which has an anti-reflective coating for the pump laser beam and a highly reflective coating for radiations emitted in the resonator cavity, which possess a desired laser emitted by the gain medium, wherein the input coupler comprises an individual coupler or a coating directly on an end-side of the gain medium;
an intracavity holder attaching the gain medium and a Q-switch, wherein the intracavity holder is precisely mounted on the laser base, the Q-switch is placed perpendicularly or at a Brewster's angle to an optical line, wherein the Q-switch is placed separately or coated directly on another side of the gain medium that is opposite to the input coupler, the optical line is defined as a line perpendicular to the input coupler and output coupler which simultaneously is a symmetry axis of the gain medium;
the gain medium is made of a lass doped with ions Er3+ and Yb3+, wherein a laser beam with the desired wavelength will be emitted under the excitation by the pump laser beam,
the Q-switch comprises a passive Q-switch is made of Co2+:MgAl2O4 crystal as a laser on/off switch and is placed perpendicularly or at Brewster's angle to the optical line in the resonator cavity,
the output coupler is coated to allow the laser beam to transmit partially, a part of the laser beam is reflected into the resonator cavity while a remaining part of the laser beam exits from the resonator cavity with a desired pulse energy.

### Claim 2 (depends on 1)

The configuration of claim 1, wherein the gain medium is made of Er:Yb doped glass with an Er concentration in a range of 0.3×1020 to 0.5×1020 cm−3, a Yb concentration in a range of 1.7×1021 to 2×1021 cm−3, a gain medium radius REr:Yb of 0.5 mm≤REr:Yb≤1, mm and a gain medium length LEr:Yb, of 5 mm≤LEr:Yb≤8 mm.

### Claim 3 (depends on 1)

The configuration of claim 1, wherein the end pumped laser transmitter has a mechanical length between the input coupler and the output coupler of 15 mm≤LKÐ≤30 mm.

### Claim 4 (depends on 1)

The configuration of claim 1, wherein the Q-switch is made of Co2+:MgAl2O4 crystal with an initial transmittance, T0, of 85%≤T0≤92% and a reflectivity of output coupler ≤85% at wavelength 1525 nm-1570 nm.

### Claim 5 (depends on 1)

The configuration of claim 1, with the coupling lenses that can adjust positions of an individual lens to change the diameter DB, or cross-section dimensions, a, b, of the pump laser beam from laser diode source in the range: 0.5 mm≤DB, a, b≤1 mm.