Mid-IR Laser Oscillation in Cr:ZnSe Planar Waveguide
Structures and in Cr:ZnSe/As
2
S
3
:As
2
Se
3
composite materials
J.E. Williams
1
, J.T. Goldstein
2
, D.V. Martyshkin
1,3
, V.V. Fedorov
1,3
, I.S. Moskalev
3
, R. Camata
1
, S.B. Mirov
1,3
1)
Center for Optical Sensors and Spectroscopies and the Department of Physics, University of Alabama at Birmingham, CH 310,
1300 University Blvd., Birmingham, AL 35294, USA
2)
Air Force Research lab, Materials and Manufacturing Directorate, AFRL/RXPSO, 3005 Hobson Way, WPAFB, Dayton, OH 45433
3)
Photonics Innovations, Inc
*
, 1500 1st Ave N, Unit 39, Birmingham, AL 35203, USA
Abstract: New transition metal doped ZnSe/As
2
S
3
:As
2
Se
3
composite materials are proposed for mid-IR
fiber-lasers. Mid-IR room-temperature lasing of Cr:ZnSe/As
2
S
3
:As
2
Se
3
micro-composite material and
Cr:ZnSe planar waveguide structures is demonstrated at 2.6 and 2.4 μm.
©2010 Optical Society of America
OCIS codes: (060.2290) Fiber materials; (230.7390) Waveguides, planar; (140.3070) Infrared and far-infrared lasers; (140.5680)
Rare earth and transition metal solid-state lasers
1 Introduction
Recent progress in chromium doped II-VI semiconductor materials (ZnS, ZnSe, CdSe) makes them the laser sources
of choice when one needs a compact system with tunability over 1.9–3.6 μm [1]. Output powers exceeding 10W and
efficiency up to 70% were demonstrated in several Cr doped semiconductors (ZnS, ZnSe). A further increase of the
output power requires thorough thermal management in the active element. Among different approaches to control
beam quality and thermal lensing, a waveguide and fiber lasers are very promising for variety of applications. In this
paper, we report first demonstration of mid-IR lasing in Cr:ZnSe waveguide structures and the first laser oscillation
of the Cr:ZnSe/As
2
S
3
:As
2
Se
3
composite materials. These composite materials are very promising for mid-IR fiber-
laser applications.
Cr:ZnSe films on the Sapphire (SAP) and GaAs substrates were fabricated using pulse laser deposition (PLD).
A Cr:ZnSe ceramic target had a total chromium concentration of 10
20
cm
-3
.
Figure 1.B shows absorption spectrum of
the Cr:ZnSe film deposited on the SAP substrate. The interference pattern reveals a good homogeneous film with a
thickness of 7.5 μm. The absorption dip near 1.7 μm results from the
5
T
2
5
E transition of Cr
2+
ions. The chromium
concentration in the film calculated from absorption was as high as N
Cr
=6·10
19
cm
-3
.
The mid-IR photoluminescence (PL) spectra, PL kinetics and lasing spectra were measured under 1560 nm
D
2
-Raman shifted Nd:YAG laser excitation with the pulse duration of 5 ns (see Fig. 1.C). As one can see from the
measurements at low pump energy the measured PL spectrum (Fig1.C curve i) is typical for the
5
T
2
5
E chromium
transition in the ZnSe host. Further increase of the pump energy above the threshold results in appearance of
intensive, much narrower stimulated emission with a central peak (2550 nm) shifted to the longer wavelengths with
respect to PL peak (Fig1.C curve ii). This shift results from the trade-off between maximum emission cross-section
at ~2400 nm and optical losses in the waveguide due to non-saturated chromium absorption. The output–input
characteristics demonstrated the threshold-like behavior of the output signal with the energy threshold at 0.5 mJ/cm
2
.
In addition, an experimental details will be reported at conference on feasibility of these Cr:ZnSe thin-film structures
for passive Q-switching and mode-locking of Er, Tm and Ho laser cavities.
Fig 1. Cr:ZnSe thin-films on sapphire substrate (A), absorption spectrum (B); and Photoluminescence (C) below
(curve i) and above (ii) laser threshold.
*
Currently a part of IPG Photonics Corporation, www.ipgphotonics.com
a401_1.pdf
FThL3.pdf
© 2010 OSA /FiO/LS 2010
FThL3.pdf