Saturable absorbers for Q-switching of middle infrared laser cavaties

Patent metadata

Field	Value
Publication number	US-9391424-B2
Application number	US-201414469547-A
Country	US
Kind code	B2
Filing date	Aug 26, 2014
Priority date	Sep 20, 2001
Publication date	Jul 12, 2016
Grant date	Jul 12, 2016

Abstract

This disclosure demonstrates successfully using single, polycrystalline, hot pressed ceramic, and thin film Fe doped binary chalcogenides (such as ZnSe and ZnS) as saturable absorbing passive Q-switches. The method of producing polycrystalline ZnSe(S) yields fairly uniform distribution of dopant, large coefficients of absorption (5-50 cm −1 ) and low passive losses while being highly cost effective and easy to reproduce. Using these Fe 2+ :ZnSe crystals, stable Q-switched output was achieved with a low threshold and the best cavity configuration yielded 13 mJ/pulse single mode Q-switched output and 85 mJ in a multipulse regime.

First claim

What is claimed is:

1. A method for producing laser pulses at a laser wavelength around 3 μm based on passive Q switching at room temperature, the method comprising:
providing a laser cavity in an Erbium or transition metal doped laser to include a doped laser gain material to produce laser light at a laser wavelength around 3 μm under optical pumping; and
using a saturable absorber inside the laser cavity to effectuate passive Q-switching in the laser light that generates laser pulses at the laser wavelength around 3 μm, where the saturable absorber is a single crystalline or polycrystalline material of Fe 2+ :ZnSe or Fe 2+ :ZnS structured to exhibit a saturable absorption at the laser wavelength around 3 μm that effectuates the passive Q-switching at room temperature.

2. The method of claim 1 , wherein the laser wavelength is in the range 2.5 μm to 3.4 μm.

3. The method of claim 1 , wherein the laser wavelength is in the range 2.5 μm to 4 μm.

4. The method of claim 1 , wherein:
the single crystalline or polycrystalline material of Fe 2+ :ZnSe or Fe 2+ :ZnS is structured to exhibit an absorption cross section of about 10 −18 cm 2 for saturable absorption at the laser wavelength around 3 μm and at the room temperature.

5. The method of claim 1 , wherein the saturable absorber is formed by:
forming a polycrystalline or single crystalline structure of a thickness sufficient for use as a microchip saturable absorber, where the polycrystalline or single crystalline structure is selected from the group consisting of ZnS and ZnSe;
depositing a thin film layer of Fe on opposing faces of the polycrystalline or single crystalline structure by a method selected from the group consisting of pulsed laser deposition, cathode arc deposition, thermal evaporation, and plasma sputtering; and
annealing the polycrystalline or single crystalline structure sealed in vacuumed ampoules in an oven for a period and at a temperature sufficient to allow crystal doping by Fe diffusion and replacement in selected regions of the polycrystalline or single crystalline structure.

6. The method of claim 1 , wherein the saturable absorber is formed by:
forming a polycrystalline or single crystalline structure of a thickness sufficient for use as a microchip saturable absorber, where the polycrystalline or single crystalline structure is selected from the group consisting of ZnS and ZnSe; and
annealing the polycrystalline or single crystalline structure sealed in vacuumed ampoules together with iron containing chemical in an oven for a period and at a temperature sufficient to allow crystal doping by Fe diffusion and replacement in selected regions of the polycrystalline or single crystalline structure.

7. The method of claim 1 , wherein the saturable absorber is formed by a thin film of Fe doped ZnS or ZnSe grown by pulsed laser deposition, plasma sputtering, or thermal evaporation on a transparent at lasing wavelength substrate made from similar or dissimilar material.

8. The method of claim 1 , wherein said saturable absorber is fabricated by hot pressing of ZnS or ZnSe powders containing iron.

9. The method of claim 1 , wherein the laser pulses comprise single-mode Q-switch pulses, each pulse having a maximum output power of 13 mJ.

10. The method of claim 1 , wherein the pulses comprise a full width half maximum (FWHM) value in the range 65 to 100 nanoseconds.

11. The method of claim 1 , wherein the laser pulses comprise 85 mJ output pulses in a multi-pulse regime.

12. The method of claim 11 , wherein the multi-pulse regime includes between 5 and 19 pulses.

13. A method for forming a saturable absorber of a 2.5 μm to 4 μm Erbium laser including a Q-switch comprising the saturable absorber selected from the group consisting of Fe doped ZnS or ZnSe that provides saturable optical behavior at a laser wavelength between the 2.5 μm and 4 μm range of the Erbium laser, the method comprising:
forming a polycrystalline or single crystalline structure of a thickness sufficient for use as a microchip saturable absorber, where the polycrystalline or single crystalline structure is selected from the group consisting of ZnS and ZnSe;
depositing a thin film layer of Fe on opposing faces of the polycrystalline or single crystalline structure by a method selected from the group consisting of pulsed laser deposition, cathode arc deposition, thermal evaporation, and plasma sputtering; and
annealing the polycrystalline or single crystalline structure sealed in vacuumed ampoules in an oven for a period and at a temperature sufficient to allow crystal doping by Fe diffusion and replacement in selected regions of the polycrystalline or single crystalline structure.

Assignees

• Uab Research Foundation

Inventors

• Mirov Sergey B
• Gallian Andrew
• Martinez Alan
• Fedorov Vladimir V

Classifications

• H01S3/092 Primary

  of flash lamp (H01S3/0937 takes precedence {; flash lamps per se H01J61/80; circuit arrangements for operating flash lamps in general H05B41/30}) · CPC title

• H01S3/1698

  rare earth · CPC title

• H01S3/1696

  transition metal · CPC title

• H01S3/1608

  erbium · CPC title

• G02F1/3523

  Non-linear absorption changing by light, e.g. bleaching · CPC title