Highly doped fiber lasers and amplifiers

Details Highly doped fiber lasers and amplifiers Highly doped fiber lasers and amplifiers

1999-04-30

2003-01-21

Lee, John D. (Department: 2874)

Optical waveguides

Having particular optical characteristic modifying chemical...

Of waveguide core

C385S123000, C372S006000, C359S341100, C359S342000

Reexamination Certificate

active

06510276

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to waveguide lasers and amplifiers based on low phonon energy glasses or crystals doped with external or impurity atoms or ions, and more particularly to devices using waveguides based on such glasses that incorporate high concentration of atoms or ions.
2. Description of the Prior Art
Because of the strong water absorption near 3 &mgr;m in tissue and the consequent ultrashort penetration depths (of a few microns), compact high power (100 mW to 1 W) 2.7 &mgr;m laser sources with TEM
00
beam quality have several important applications in ultrafine intra-ocular and endoscopic laser surgery including transmyocardial revascularization and other intra-arterial procedures. In such applications, laser energy absorbed by the targeted tissue is capable of its coagulation or precise ablation with minimal damage to the remaining tissue. Other applications that could benefit from compact and efficient sources of mid-IR radiation include infrared countermeasures and spectroscopic sensing.
A broadly tunable 2.7 &mgr;m transition in Er:ZBLAN appears particularly attractive for the design of compact, high power CW fiber lasers of excellent beam quality, as needed for the above-identified applications ranging from endoscopic laser surgery to countermeasures and spectroscopic monitoring. It is well known that the longer lifetime of the lower laser level (
4
I
13/2
, 9.4 ms) compared to the upper laser level (
4
I
11/2
, 7.5 ms) of this transition poses a serious bottleneck in such Er:ZBLAN lasers. This bottleneck has been alleviated by complex mechanisms such as: (1) selective depletion of the lower laser level via excited state absorption (ESA), and (2) cascade lasing. None of these solutions offer a commercially viable Er:ZBLAN laser.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved highly doped fiber laser and/or amplifier that will provide high efficiency and high power output.
It is a further object to provide a highly doped fiber laser and/or amplifier which greatly reduces or eliminates the bottleneck associated with the longer lifetime of the lower laser level
4
I
13/2
if Er is used as a dopant.
It is yet another object to provide a fiber laser and/or amplifier that has a dopant at a concentration level that results in clusters of such dopants.
It is yet another object to provide highly doped fiber laser and/or amplifier having a dopant that greatly enhances cross-relaxation.
It is yet another object to provide highly doped fiber laser and/or amplifier having a dopant that greatly enhances cross-relaxation by creating ion or dopant clusters.
It is yet another object to provide sensitizer ions or atoms to assist in the depopulation of lower energy levels through the energy transfer process.
In all of the above embodiments, it is an object to provide a highly doped fiber laser and/or amplifier that has a dopant concentrations between 1,001 and 149,999 ppm.
According to one broad aspect of the present invention, there is provided a highly doped waveguide comprising: a waveguide having a dopant disposed therein, the dopant having a concentration of between 1,001 and 500,000 ppm; and wherein the concentration of the dopant enhances cross-relaxation between two elements of the dopant.
According to another broad aspect of the invention, there is provided a highly doped waveguide comprising: a waveguide having a dopant disposed therein, the dopant having a concentration of between 1,001 and 500,000 ppm, the dopant being Er; wherein the waveguide is composed of material selected from the group comprising: GaN, ZnS, AlAs, GaAs, ZnSe, YLF, BaYF, ZrF
4
, HfF
4
, BaF
2
, SrF
2
, LaF
3
, YF
3
, AlF
3
, KF, NaF, LiF, chalcogenides, tellurides, silicates, and chelates; and wherein the concentrations of the dopant enhances cross-relaxation between two elements of the dopant.
According to another broad aspect of the invention, there is provided A highly doped waveguide laser comprising: a low phonon energy waveguide having a dopant disposed therein, the dopant having a concentration of between 1,001 and 500,000 ppm, the dopant being Er; a resonant cavity, the resonant cavity being defined by a first and second reflective means at an amplification wavelength and disposed at opposite ends of the waveguide; an energy source for injecting energy into the waveguide; and wherein the concentrations of the dopant enhances cross-relaxation between two elements of the dopant.
According to another broad aspect of the invention, there is provided a highly doped waveguide amplifier comprising: a low phonon energy waveguide having a dopant disposed therein, the dopant having a concentration of between 1,001 and 500,000 ppm, the dopant being Er; an energy source for injecting energy into the waveguide and thereby forming a highly doped waveguide amplifier; and wherein the dopant enhances cross-relaxation between two elements of the dopant.
According to another broad aspect of the invention, there is provided a highly doped optical material comprising: a low phonon energy bulk material having a dopant disposed therein, the dopant having a concentration of between 100 and 150,000 ppm, the waveguide containing clusters of the dopant; and wherein the clusters enhance cross-relaxation between two elements of the dopant.
According to another broad aspect of the invention, there is provided a highly doped bulk material laser comprising: a low phonon energy bulk material having a dopant disposed therein, the dopant having a concentration of between 100 and 150,000 ppm, the bulk material containing clusters of the dopant; the dopant being Er; a resonant cavity, the resonant cavity being defined by a first and second reflective means at an amplification wavelength and disposed at two ends of the bulk material; an energy source for injecting energy into the bulk material; and wherein the dopant enhances cross-relaxation between two elements of the dopant.
According to another broad aspect of the invention, there is provided a highly doped bulk material amplifier comprising: a low phonon energy bulk material having a dopant disposed therein, the dopant having a concentration of between 100 and 150,000 ppm, the dopant being Er; an energy source for injecting energy into the bulk material and thereby forming a highly doped bulk material amplifier; and wherein the dopant enhances cross-relaxation between two elements of the dopant.
Other objects and features of the present invention will be apparent from the following detailed description of the preferred embodiment.


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Kintz et al, “cw and pulsed 2.8 &mgr;m laser emission from diode-pumped Er: YLF at room temperature,”appl. Phys. Lett.50 (22), Jun. 1, 1987, pp. 1553-1555.
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