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AssigneeLucent Technologies Inc.
InventorsFederico Capasso, Alfred Yi Cho, Claire F. Gmachl, Milton L. Peabody, Arthur Mike Sergent, Deborah Lee Sivco, Alexander Soibel
Estimating the term…
Term ended 25 Apr 2024 (estimated)
A broadband CLE capable of operation simultaneously at multiple wavelengths comprises: a core region including a multiplicity or cascade of stages, each stage including a radiative transition region. A first group of stages emits radiation at a first wavelength and at a first aggregate intensity per group, and a second group of stages emits radiation at a second wavelength and at a second aggregate intensity per group lower than the first intensity. The invention is characterized in that the second group has more stages than said first group, and the per-stage intensity of the first group is greater than that of the second group. This design reduces the difference between said first and second aggregate intensities. In one embodiment, groups that are located at or near to the ends of the cascade have more stages than groups that are centrally located within the cascade regardless of their wavelength. Our invention significantly reduces variations in modal gain across the desired broadband spectrum and produces sufficiently flat gain without requiring elaborate redesign of the stages. These features enable cw operation of a broadband intersubband laser.
A broadband CLE capable of operation simultaneously at multiple wavelengths comprising:
A quantum cascade laser comprising:
A method of fabricating a broadband CLE capable of operation simultaneously at multiple wavelengths comprising the steps of:
Dependencies are inferred from the claim text.
Drawings are temporarily unavailable. Open the PDF at USPTO
Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or…:…
Nanooptics
Semiconductor lasers: arrangements for controlling the laser output parameters, e.g. by operating on the active medium
Multi-wavelength lasing: in a single cavity
From the US filing history. Foreign family members aren’t listed.
1. Field of the Invention
This invention relates to semiconductor cascade light emitters (CLEs) in general and, more particularly, to broadband intersubband (ISB) [e.g., quantum cascade (QC)] lasers adapted for continuous wave (cw) operation.
2. Discussion of the Related Art
Our invention, together with its various features and advantages, can be readily understood from the following more detailed description taken in conjunction with the accompanying drawing, in which:
FIG. 1 is a schematic, cross-sectional view of an ISB laser in accordance with an illustrative embodiment of our invention;
FIG. 2 is a graph illustrating the variation of optical intensity with wavelength across a cascade of RT regions, as well as the variation of the number of stages with wavelength within the cascade, in an ISB laser in accordance with one embodiment of our invention;
General Structure
With reference now to FIG. 1, a prior art homogeneous ISB semiconductor light emitter (e.g., a QC laser) 10 comprises a core region 14 sandwiched between an upper cladding region 16 and a lower cladding region 12. The core region includes the active region of the laser. The active region, in turn, includes a multiplicity of essentially identical repeat units or stages; that is, the overall device is termed homogeneous. In a typical design, each stage includes a radiative transition (RT) region and an adjacent injection/relaxation (I/R) region. Alternatively, each stage may include an RT region sandwiched between an I-region and a R-region, as described in U.S. Pat. No. 6,324,199 issued on Nov. 27, 2001 (Capasso et al. 56-91-9-9-21-25-6), which is assigned to the assignee hereof and incorporated herein by reference. When the light emitter is designed to operate at a single center wavelength, all of its stages are essentially identical to one another. However, when the light emitter is designed to operate simultaneously at multiple center wavelengths, the stages are designed in accordance with our invention, as described in the next section.
The term ISB in general refers to the well-known unipolar nature of the optical and electronic transitions that take place in the RT and I/R regions.