ABSTRACT: Thin film slab waveguides of lanthanum fluoride clad with
strontium fluoride grown epitaxially on GaAs (111) are characterized by
optical and structural techniques. Crystallinity, surface roughness,
refractive indexes and propagation loss measurements suggest that these
structures show promise for monolithically integrated infrared (IR)
pumped IR down-conversion and visible upconversion laser devices.
Propagation losses as low as 3.7 dB/cm at 633 nm were measured in
samples which show waveguide propagation over distances of several
centimeters. Simulation of the scattering losses due to surface
roughness provides an approximate delineation of surface and nonsurface
contributions to the optical loss. Typical root-mean-square surface
roughness of the lanthanum fluoride layer was on the order of 3 nm. The
morphology appears to be dominated by grain boundaries
Journal of Lightwave Technology 05/1996; · 2.78 Impact Factor
ABSTRACT: We have grown planar waveguides of rare earth doped single crystal
fluoride films on insulating and semiconductor substrates using
molecular beam epitaxy and have formed channel waveguides by ion
milling. Structural and spectral analysis demonstrates that excellent
crystallinity is being achieved and that the rare earth ion is
incorporated into the film at sites and in charge states similar to bulk
laser hosts. Lifetime measurements confirm that the local environment of
the dopant ion is essentially that found for bulk materials. Single and
higher order optical mode propagation has been demonstrated for the
channel waveguides. By exciting individual channels with an 800 nm pump,
we have generated strong upconversion fluorescence in Er and Nd doped
guides. The ability to fabricate these waveguides On semiconductor
substrates substantiates the potential for on chip integration of both
IR downconversion lasers and IR pumped upconversion visible and UV
lasers with a diode laser pump source. The use of transition metal
dopants is possible and would enable tunable operation. Waveguide
propagation loss in present devices must be reduced to realize a laser
oscillator and we discuss how this is being addressed
IEEE Journal of Selected Topics in Quantum Electronics 05/1995; · 3.78 Impact Factor
ABSTRACT: Planar waveguides of erbium doped ZnF<sub>2</sub> on MgF<sub>2</sub> substrate have been grown using molecular beam epitaxy and channel waveguides have been formed by ion milling. By exciting individual channels with an 800 nm pump, strong upconversion fluorescence has been generated at 410, 550 and 670 nm and at numerous weaker peaks. The fabrication technique can be adapted to semiconductor substrates for making compact diode-pumped visible and infra-red lasers.
Electronics Letters 02/1993; · 0.96 Impact Factor
ABSTRACT: Waveguide structures offer the possibility of making an upconversion laser operating at room temperature. By reducing the optical mode cross section can lead to a very high pump power density which allows modest pumping powers to overcome non-radiative decay processes. We have reported earlier on the observation of upconversion luminescence from both planar and channel waveguides of Erbium doped ZnF2 on MgF2(001) and Erbium doped PbF2 on GaAs(100). The epitaxial fluoride layers were all grown by Molecular Beam Epitaxy. Fluoride films preferentially grow on the (111) GaAs surface. In order to exploit this fact, we have grown Erbium doped PbF2 on GaAs(111)B with an intervening SrF2 cladding layer. The SrF2 and PbF2 growth conditions have been optimized on GaAs(111)B using X-ray rocking curve analysis. The crystalline quality of the films grown on GaAs(111)B are far superior to those grown on GaAs(100). Upconversion luminescence has been observed in the PbF2: Er/SrF2/GaAs(111)B planar waveguide structures. The guide ends were formed by cleaving the semiconductor wafer and the 800nm and 980nm pump light was introduced from a Ti-Sapphire laser by end pumping using a microscope objective.
MRS Proceedings. 12/1992; 329.
ABSTRACT: With the recent success of using rare-earth doped fluoride crystals as high power visible upconversion lasers, we have explored the use of MBE grown fluoride layers for a possible waveguide laser. By confining the pumped light in a waveguide with dimensions on the order of a few micron, the pump power density will increase promoting higher efficiencies at room temperatures. Initially, we have grown planar waveguides of erbium doped ZnF2 on MgF2 substrates using molecular beam epitaxy and have formed channel waveguides by ion milling. By exciting individual channels with an 800 nm pump, we have generated strong upconversion fluorescence at 410 nm, 550 nm and 670 nm and at numerous weaker peaks. The fabrication techniques can be adapted to semiconductor substrates for making compact diode-pumped visible and infrared lasers. A number of fluoride materials that are useful as laser host crystals are lattice matched to GaAs (100) and GaAs (111) offering the possibility of integrating the channel waveguide laser with the semiconductor diode laser pump source. For example SrF2 may be grown on GaAs (100) as a cladding layer followed by PbF2 doped with a rare-earth ion. Also LaF3 may be grown on GaAs (111) followed by CeF3 doped with a rare-earth ion. Both PbF2 and CeF3 have low phonon energies and a higher index of refraction than their respective lattice matched cladding layers and should be capable of provide an attractive upconversion laser waveguide system. Our initial upconversion luminescence results on erbium doped PbF2 on GaAs (100) using a intervening SrF2 cladding layer are also reported.
MRS Proceedings. 12/1992; 301.