摘要:
Semiconductor optoelectronic devices such as diode lasers are formed on InP substrates with an active region with an InAsN or InGaAsN electron quantum well layer and a GaAsSb or InGaAsSb hole quantum well layer which form a type II quantum well. The active region may be incorporated in various devices to provide light emission at relatively long wavelengths, including light emitting diodes, amplifiers, surface emitting lasers and edge-emitting lasers.
摘要:
A surface-emitting photonic crystal distributed feedback laser apparatus configured to emit an optical beam of light. The apparatus includes a laser cavity bounded by top and bottom optical claddings, an active region configured to produce optical gain upon receiving optical or electrical pumping, a periodic two-dimensional grating having an order higher than the fundamental and configured to induce modulation of a modal refractive index, and lateral pumped gain area contained within an area covered by the grating, the lateral pumped gain area configured to produce gain in one or more lasing modes having a modal index modulated by the grating. The lateral pumped gain area has a substantially circular shape of diameter D, and wherein the pumped gain area is enclosed by an unpumped region contained within the area covered by the grating but not receiving the optical or electrical pumping.
摘要:
A gain region for an interban quantum well laser incudes (a) an emitter ron of semiconductor material having at least one conduction subband and at least one valence subband, these subbands being spaced apart by an energy band-gap; (b) a collector region of semiconductor material having at least one conduction subband and at least one valence subband, these subbands spaced apart by an energy band-gap; (c) a type-I or type-II active region; and (d) a blocking quantum well region of semiconductor material between the active region and the collector region, for keeping electrons in the active region from tunnelling or scattering into the collector region, but allowing electrons in the highest valence subband in the active region to pass into the collector region. Another aspect of the invention is a cascade laser made from a stack of these gain regions, connected in series, optical cladding regions at opposing ends of the stack, and a voltage source for applying a bias voltage to the stack, and an optical cavity perpendicular to the stacking axis fabricated by cleaving or other means.
摘要:
A photonic-crystal distributed-feedback laser includes a laser cavity with a waveguide structure that has a cavity length Lc and is bounded by two mirrors; an active region for producing optical gain upon receiving optical pumping or an input voltage; at least one layer having a periodic two-dimensional grating with modulation of a modal refractive index, the grating being defined on a rectangular lattice with a first period along a first axis of the grating and a second period along a second perpendicular axis of the grating, and wherein the grating produces three diffraction processes having coupling coefficients κ1′, κ2′, κ3′; and a lateral gain area contained within a second area patterned with the grating that has substantially a shape of a gain stripe with a width W, with the gain stripe tilted at a first tilt angle relative to the two mirrors. The rectangular lattice of the grating is tilted at a second tilt angle substantially the same as the first tilt angle with respect to the gain stripe, and the ratio of the first and second grating periods is equal to the tangent of the first tilt angle, with the first tilt angle being between about 16° and about 23°. The hexagonal lattice does not need to be tilted with respect to the two mirrors. The laser's output emerges along the normal to a facet irrespective of the operating laser wavelength, facilitating coupling the laser light into a fiber or other optical system while avoiding beam steering. The two-dimensional nature of the feedback in the laser provides for varying the wavelength through angle tuning. Wavelength tuning by changing the propagation direction (propagation angle) permits a straightforward selection of different wavelengths from photonic crystal devices monolithically fabricated on a single wafer. The fabrication procedure is straightforward since no ridges need to be defined. The single-mode spectral purity of the rectangular-lattice PCDFB is robust, owing to the near absence of side modes, and exhibits good beam quality.
摘要:
A method for calculating the beam quality and output wavelength spectrum of a photonic crystal distributed feedback laser includes the steps of calculating at least two coupling coefficients and forming a characteristic matrix; repeating the following steps at spaced increments of time until a steady state solution is reached: repeating the following steps for one of the incremental cavity lengths: calculating a gain change and a modal refractive index change for the laser waveguide structure for one incremental stripe width; calculating a spontaneous emission term for the gain change; calculating a gain roll-off term for the gain change; applying the gain change, the modal refractive index change, the spontaneous emission term, and the gain roll-off term to at least two forward-propagating beams and at least two backward-propagating beams for the one incremental stripe width; performing a Fourier transformation with respect to the one incremental stripe width to yield a plurality of diffraction terms; adding the diffraction terms to the characteristic matrix; propagating the two forward-propagating beams by the incremental cavity length from a first section to a succeeding and adjacent second section with the characteristic matrix; propagating the two backward-propagating beams by the incremental cavity length from the second section to the first section with the characteristic matrix; performing an inverse Fourier transformation with respect to the stripe width; and applying at least one boundary condition to a facet of the laser configuration for each time increment. The steady-state solution is used as the basis for evaluating the beam quality and output wavelength spectrum corresponding to the design parameters, the additional design parameters, and the photonic crystal geometry of the laser configuration. The invention provides scientists with an approach to designing and building lasers that eliminates much of the time and resources otherwise needed in the building and testing of unsuccessful designs.
摘要:
A configuration that promotes cleaner fracture by reducing or eliminating secondary fractures includes a plurality of distinct interconnecting regions defining a plurality of separate fracture regions that are separated by an interruption.