Laser-based projectors are gaining increased acceptance in mobile device market due to their low ... more Laser-based projectors are gaining increased acceptance in mobile device market due to their low power consumption, superior image quality and small size. The basic configuration of such micro-projectors is a miniature mirror that creates an image by raster scanning the collinear red, blue and green laser beams that are individually modulated on a pixel-bypixel basis. The image resolution of these displays can be limited by the modulation bandwidth of the laser sources, and the modulation speed of the green laser has been one of the key limitations in the development of these displays. We will discuss how this limitation is fundamental to the architecture of many laser designs and then present a green laser configuration which overcomes these difficulties. In this green laser architecture infra-red light from a distributed Bragg-reflector (DBR) laser diode undergoes conversion to green light in a waveguided second harmonic generator (SHG) crystal. The direct doubling in a single pas...
The 16th Annual Meeting of the IEEE Lasers and Electro-Optics Society, 2003. LEOS 2003.
This paper extensively studies the design and resulting performance of high power EDFA pump laser... more This paper extensively studies the design and resulting performance of high power EDFA pump lasers to increase the operating power with each generation of chip developed while maintaining or improving other critical design features.
Localized quantum walks are theoretically investigated in new class of quasiperiodic photonics la... more Localized quantum walks are theoretically investigated in new class of quasiperiodic photonics lattices. Theoretical results have been validated quantitatively by experiments of quantum walks in Fibonacci multicore fibers.
Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, 2009
Rapid progress in green laser technology is enabling laser light sources to become the ideal ligh... more Rapid progress in green laser technology is enabling laser light sources to become the ideal light sources for micro-projection displays, where the size and power efficiency of the display creates a new display category. Article not available.
Proquest Dissertations and Theses Thesis University of Massachusetts Amherst 1997 Publication Number Aai9737554 Isbn 9780591474923 Source Dissertation Abstracts International Volume 58 06 Section B Page 3230 209 P, 1997
Stimulated emission, lasing, and related properties of III-V nitride heterostructures are studied... more Stimulated emission, lasing, and related properties of III-V nitride heterostructures are studied. A strain-dependent semi-empirical tight-binding model is developed, using the valence force-field model of Keating, to predict the atomic positions in the strained wurtzite crystal lattice. Predicted deformation potentials and strain-induced exciton splitting are shown to closely match data in the literature. The spectral properties of the edge luminescence from GaN-AlGaN heterostructures is investigated. The existence of stimulated emission is demonstrated and a measurement of the optical gain spectra is reported. In addition, the light emission properties of GaN-AlGaN separate confinement heterostructures is studied. The measured luminescence properties are improved for active region designs with fewer, thicker wells. An analysis of the trend is presented demonstrating recombination at the well-barrier interface as a significant factor. The results also indicate that the quantum wells experience compressive strain from the lattice mismatch with the AlGaN cladding layers. Further experimental results demonstrate that the commonly observed surface stimulated emission is related to in-plane optical gain, and is observed most commonly in samples with rough surface morphology. Photopumping results from GaN-AlGaN laser platelets are presented and discussed. Laser oscillation in GaN-AlGaN separate confinement heterostructures is demonstrated in which the optical cavity is formed unintentionally by parallel cracks in the epilayer. The observed laser modes are broad and shift to shorter wavelengths with increasing pump intensity. An analysis is presented revealing that mode shifting resulting from carrier-induced refractive index changes restricts the observation of laser modes to short optical cavities. GaN-AlGaN Bragg reflectors are investigated through reflectivity modeling and characterization. A transfer-matrix model is developed with an empirical relation for the refractive indices and predictions of the model are compared with data in the literature. Experimental results are then presented and compared with the predictions of the model. The design and characterization of GaN-AlGaN vertical cavity surface emitting lasers is studied. Luminescence spectra are presented from two devices which demonstrate sharp, highly-polarized, regularly spaced modes for pump intensities above a threshold. The spacing of the laser modes is shown to match the mode spacing predicted by the reflectivity model
Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications IX, 2010
ABSTRACT Laser-based projectors are gaining increased acceptance in mobile device market due to t... more ABSTRACT Laser-based projectors are gaining increased acceptance in mobile device market due to their low power consumption, superior image quality and small size. The basic configuration of such micro-projectors is a miniature mirror that creates an image by raster scanning the collinear red, blue and green laser beams that are individually modulated on a pixel-bypixel basis. The image resolution of these displays can be limited by the modulation bandwidth of the laser sources, and the modulation speed of the green laser has been one of the key limitations in the development of these displays. We will discuss how this limitation is fundamental to the architecture of many laser designs and then present a green laser configuration which overcomes these difficulties. In this green laser architecture infra-red light from a distributed Bragg-reflector (DBR) laser diode undergoes conversion to green light in a waveguided second harmonic generator (SHG) crystal. The direct doubling in a single pass through the SHG crystal allows the device to operate at the large modulation bandwidth of the DBR laser. We demonstrate that the resultant product has a small footprint (9% electrical-to-optical conversion) and large modulation bandwidth (>100 MHz).
Laser-based projectors are gaining increased acceptance in mobile device market due to their low ... more Laser-based projectors are gaining increased acceptance in mobile device market due to their low power consumption, superior image quality and small size. The basic configuration of such micro-projectors is a miniature mirror that creates an image by raster scanning the collinear red, blue and green laser beams that are individually modulated on a pixel-bypixel basis. The image resolution of these displays can be limited by the modulation bandwidth of the laser sources, and the modulation speed of the green laser has been one of the key limitations in the development of these displays. We will discuss how this limitation is fundamental to the architecture of many laser designs and then present a green laser configuration which overcomes these difficulties. In this green laser architecture infra-red light from a distributed Bragg-reflector (DBR) laser diode undergoes conversion to green light in a waveguided second harmonic generator (SHG) crystal. The direct doubling in a single pas...
The 16th Annual Meeting of the IEEE Lasers and Electro-Optics Society, 2003. LEOS 2003.
This paper extensively studies the design and resulting performance of high power EDFA pump laser... more This paper extensively studies the design and resulting performance of high power EDFA pump lasers to increase the operating power with each generation of chip developed while maintaining or improving other critical design features.
Localized quantum walks are theoretically investigated in new class of quasiperiodic photonics la... more Localized quantum walks are theoretically investigated in new class of quasiperiodic photonics lattices. Theoretical results have been validated quantitatively by experiments of quantum walks in Fibonacci multicore fibers.
Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, 2009
Rapid progress in green laser technology is enabling laser light sources to become the ideal ligh... more Rapid progress in green laser technology is enabling laser light sources to become the ideal light sources for micro-projection displays, where the size and power efficiency of the display creates a new display category. Article not available.
Proquest Dissertations and Theses Thesis University of Massachusetts Amherst 1997 Publication Number Aai9737554 Isbn 9780591474923 Source Dissertation Abstracts International Volume 58 06 Section B Page 3230 209 P, 1997
Stimulated emission, lasing, and related properties of III-V nitride heterostructures are studied... more Stimulated emission, lasing, and related properties of III-V nitride heterostructures are studied. A strain-dependent semi-empirical tight-binding model is developed, using the valence force-field model of Keating, to predict the atomic positions in the strained wurtzite crystal lattice. Predicted deformation potentials and strain-induced exciton splitting are shown to closely match data in the literature. The spectral properties of the edge luminescence from GaN-AlGaN heterostructures is investigated. The existence of stimulated emission is demonstrated and a measurement of the optical gain spectra is reported. In addition, the light emission properties of GaN-AlGaN separate confinement heterostructures is studied. The measured luminescence properties are improved for active region designs with fewer, thicker wells. An analysis of the trend is presented demonstrating recombination at the well-barrier interface as a significant factor. The results also indicate that the quantum wells experience compressive strain from the lattice mismatch with the AlGaN cladding layers. Further experimental results demonstrate that the commonly observed surface stimulated emission is related to in-plane optical gain, and is observed most commonly in samples with rough surface morphology. Photopumping results from GaN-AlGaN laser platelets are presented and discussed. Laser oscillation in GaN-AlGaN separate confinement heterostructures is demonstrated in which the optical cavity is formed unintentionally by parallel cracks in the epilayer. The observed laser modes are broad and shift to shorter wavelengths with increasing pump intensity. An analysis is presented revealing that mode shifting resulting from carrier-induced refractive index changes restricts the observation of laser modes to short optical cavities. GaN-AlGaN Bragg reflectors are investigated through reflectivity modeling and characterization. A transfer-matrix model is developed with an empirical relation for the refractive indices and predictions of the model are compared with data in the literature. Experimental results are then presented and compared with the predictions of the model. The design and characterization of GaN-AlGaN vertical cavity surface emitting lasers is studied. Luminescence spectra are presented from two devices which demonstrate sharp, highly-polarized, regularly spaced modes for pump intensities above a threshold. The spacing of the laser modes is shown to match the mode spacing predicted by the reflectivity model
Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications IX, 2010
ABSTRACT Laser-based projectors are gaining increased acceptance in mobile device market due to t... more ABSTRACT Laser-based projectors are gaining increased acceptance in mobile device market due to their low power consumption, superior image quality and small size. The basic configuration of such micro-projectors is a miniature mirror that creates an image by raster scanning the collinear red, blue and green laser beams that are individually modulated on a pixel-bypixel basis. The image resolution of these displays can be limited by the modulation bandwidth of the laser sources, and the modulation speed of the green laser has been one of the key limitations in the development of these displays. We will discuss how this limitation is fundamental to the architecture of many laser designs and then present a green laser configuration which overcomes these difficulties. In this green laser architecture infra-red light from a distributed Bragg-reflector (DBR) laser diode undergoes conversion to green light in a waveguided second harmonic generator (SHG) crystal. The direct doubling in a single pass through the SHG crystal allows the device to operate at the large modulation bandwidth of the DBR laser. We demonstrate that the resultant product has a small footprint (9% electrical-to-optical conversion) and large modulation bandwidth (>100 MHz).
Uploads
Papers by David Loeber