A MEMS tunable VCSEL includes a membrane device having a mirror and a distal-side electrostatic cavity for displacing the mirror to increase a size of an optical cavity. A VCSEL device includes an active region for amplifying light. One or more proximal-side electrostatic cavities are defined between the VCSEL device and the membrane device and used to displace the mirror to decrease a size of an optical cavity.
H01S 5/183 - Lasers à émission de surface [lasers SE], p.ex. comportant à la fois des cavités horizontales et verticales comportant uniquement des cavités verticales, p.ex. lasers à émission de surface à cavité verticale [VCSEL]
H01S 3/105 - Commande de l'intensité, de la fréquence, de la phase, de la polarisation ou de la direction du rayonnement, p.ex. commutation, ouverture de porte, modulation ou démodulation par commande de la position relative ou des propriétés réfléchissantes des réflecteurs de la cavité
2.
TUNABLE VCSEL POLARIZATION CONTROL WITH INTRACAVITY SUBWAVELENGTH GRATING
A very strong selection mechanism is provided in a tunable vertical cavity surface emitting laser (VCSEL) by manipulating the laser threshold to be different for TE and TM polarization by a employing a subwavelength grating in the laser cavity. The laser selects the polarization with the lowest threshold. The grating does not diffract and does not add loss to the cavity. It works by creating a large birefringence layer between the semiconductor and air sub-cavities of the full VCSEL. Multilayer stack calculations show that this results in a lower threshold for the TM polarization over the TE. This subwavelength grating layer, in one embodiment, replaces the AR coating on the semiconductor surface.
H01S 5/183 - Lasers à émission de surface [lasers SE], p.ex. comportant à la fois des cavités horizontales et verticales comportant uniquement des cavités verticales, p.ex. lasers à émission de surface à cavité verticale [VCSEL]
H01S 5/343 - Structure ou forme de la région active; Matériaux pour la région active comprenant des structures à puits quantiques ou à superréseaux, p.ex. lasers à puits quantique unique [SQW], lasers à plusieurs puits quantiques [MQW] ou lasers à hétérostructure de confinement séparée ayant un indice progressif [GRINSCH] dans des composés AIIIBV, p.ex. laser AlGaAs
3.
TUNABLE VCSEL WITH STRAIN COMPENSATED SEMICONDUCTOR DBR
Tunable VCSELs (TVCSELs) employing expanded material systems with expanded mechanical/optical design space for semiconductor DBR mirrors on GaAs substrates. One is the InGaAs / AlGaAsP material system. It adds indium In to decrease InGaAs H-layer bandgap for higher refractive index and higher DBR layer refractive index contrast. Adding phosphorus P gives independent control of bandgap and strain of AlGaAsP low refractive index L-layers. The tensile strain of AlGaAsP L-layer compensates compressive strain of InGaAs H-layer and lowers the cumulative strain of the multilayer DBR structure. Another option is the InGaAsN(Sb) / AlGaAsP material system, where both types of layers can be lattice matched to GaAs. It uses indium In and nitrogen N, and possibly antimony Sb, to get independent control of strain and bandgap, and thus refractive index, of dilute nitride InGaAsN(Sb) H-layers, with lower bandgap and higher refractive index than starting GaAs. Using expanded material system enables reliable DBR mirrors with higher reflectivity and spectral bandwidth and tunable VCSELs with wider tuning range.
H01S 5/183 - Lasers à émission de surface [lasers SE], p.ex. comportant à la fois des cavités horizontales et verticales comportant uniquement des cavités verticales, p.ex. lasers à émission de surface à cavité verticale [VCSEL]
4.
OCT SYSTEM WITH BONDED MEMS TUNABLE MIRROR VCSEL SWEPT SOURCE
A microelectromechanical systems (MEMS)-tunable vertical-cavity surfaceemitting laser (VCSEL) in which the MEMS mirror is a bonded to the active region. This allows for a separate electrostatic cavity, that is outside the laser's optical resonant cavity. Moreover, the use of this cavity configuration allows the MEMS mirror to be tuned by pulling the mirror away from the active region. This reduces the risk of snap down. Moreover, since the MEMS mirror is now bonded to the active region, much wider latitude is available in the technologies that are used to fabricate the MEMS mirror. This is preferably deployed as a swept source in an optical coherence tomography (OCT) system.
G01B 9/02091 - Interféromètres tomographiques, p.ex. à cohérence optique
H01S 5/183 - Lasers à émission de surface [lasers SE], p.ex. comportant à la fois des cavités horizontales et verticales comportant uniquement des cavités verticales, p.ex. lasers à émission de surface à cavité verticale [VCSEL]
5.
OCT SYSTEM WITH TUNABLE CLOCK SYSTEM FOR FLEXIBLE DATA ACQUISITION
An OCT system and particularly its clock system generates a k-clock signal but also generates an optical frequency reference sweep signal that, for example, indicates the start of the sweep or an absolute frequency reference associated with the sweep at least for the purposes of sampling of the interference signal and/or processing of that interference signal into the OCT images. The clock system is also tunable to allow the control or flexibility over the relationship between the scanning of the swept optical signal and the sampling of the interference signal by the data acquisition system. Specifically, the absolute frequencies of the swept optical signal at which the k-clock signals are generated can be adjusted.
An OCT system and particularly its clock system generates a k-clock signal but also generates an optical frequency reference sweep signal that, for example, indicates the start of the sweep or an absolute frequency reference associated with the sweep at least for the purposes of sampling of the interference signal and/or processing of that interference signal into the OCT images. This optical frequency reference sweep signal is generated at exactly the same frequency of the swept optical signal from sweep to sweep of that signal. This ensures that the sampling of the interference signal occurs at the same frequencies, sweep to sweep.
7.
MULTI-SPEED OCT SWEPT SOURCE WITH OPTIMIZED K-CLOCK
An optical coherence tomography system utilizes an optical swept source that frequency scans at least two different sweep rates. In this way, the system can perform large depth scans of the sample and then the same system can perform shorter depth high precision scans, in one specific example. In order to optimally use the analog to digital converter that samples the interference signal, the system further samples the interference signals at different optical frequency sampling intervals depending upon the selected sweep rates of the optical swept source. This allows the system to adapt to different sweep rates in an optimal fashion.
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