Abstract:
A microelectromechanical systems (MEMS)-tunable vertical-cavity surface-emitting laser (VCSEL) in which the MEMS mirror is 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.
Abstract:
A frequency swept laser source for TEFD-OCT imaging includes an integrated clock subsystem on the optical bench with the laser source. The clock subsystem generates frequency clock signals as the optical signal is tuned over the scan band. Preferably the laser source further includes a cavity extender in its optical cavity between a tunable filter and gain medium to increase an optical distance between the tunable filter and the gain medium in order to control the location of laser intensity pattern noise. The laser also includes a fiber stub that allows for control over the cavity length while also controlling birefringence in the cavity.
Abstract:
A frequency swept laser source for TEFD-OCT imaging includes an integrated clock subsystem on the optical bench with the laser source. The clock subsystem generates frequency clock signals as the optical signal is tuned over the scan band. Preferably the laser source further includes a cavity extender in its optical cavity between a tunable filter and gain medium to increase an optical distance between the tunable filter and the gain medium in order to control the location of laser intensity pattern noise. The laser also includes a fiber stub that allows for control over the cavity length while also controlling birefringence in the cavity.
Abstract:
An optical coherence tomography system utilizes an optical swept laser that has improved coherence length in the swept optical signal. This is accomplished using an intra-cavity element that extracts the tunable optical signal at the optimal location within the laser's resonant cavity. Generally this location is between the intracavity tuning element and the cavity's gain element so that light coming from the tuning element is extracted. In general in lasers, the gain element adds noise and chirp and this degrades the tunable optical signal's coherence length.
Abstract:
An optical coherence analysis system uses a laser swept source that is constrained to operate in a stable mode locked condition by modulating a drive current to the semiconductor optical amplifier as function of wavelength or synchronously with the drive voltage of the laser's tunable element based on stability map for the laser.
Abstract:
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. Such a system is relevant to a number of applications in which it is important that successive sweeps of the swept optical signal be very stable with respect to each other.
Abstract:
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. Such a system is relevant to a number of applications in which it is important that successive sweeps of the swept optical signal be very stable with respect to each other. One specific example is phase sensitive OCT. This requires that the sampling of the interference signal occurs at exactly the same frequency/wavelength on every axial line (A-line). Such phase sensitive OCT has particular applications in Doppler OCT, synthetic aperture imaging, and in the subtraction of background noise sources from the OCT image.
Abstract:
An integrated swept wavelength tunable optical source uses a narrowband filtered broadband signal with an optical amplifier and self-tracking filter. This source comprises a micro optical bench, a source for generating broadband light, a tunable Fabry Perot filter, installed on the bench, for spectrally filtering the broadband light from the broadband source to generate a narrowband tunable signal, an amplifier, installed on the bench, for amplifying the tunable signal. The self-tracking arrangement is used where a single tunable filter both generates the narrowband signal and spectrally filters the amplified signal. In some examples, two-stage amplification is provided. The use of a single bench implementation yields a low cost high performance system. For example, polarization control between components is no longer necessary.
Abstract:
An optical probe for emitting and/or receiving light within a body comprises an optical fiber that transmits and/or receives an optical signal, a silicon optical bench including a fiber groove running longitudinally that holds an optical fiber termination of the optical fiber and a reflecting surface that optically couples an endface of the optical fiber termination to a lateral side of the optical bench. The fiber groove is fabricated using silicon anisotropic etching techniques. Some examples use a housing around the optical bench that is fabricated using LIGA or other electroforming technology. A method for forming lens structure is also described that comprises forming a refractive lens in a first layer of a composite wafer material, such as SOI (silicon on insulator) wafers and forming an optical port through a backside of the composite wafer material along an optical axis of the refractive lens. The refractive lens is preferably formed using grey-scale lithography and dry etching the first layer.
Abstract:
An optical resonator including is designed is to degrade the ability of the resonator to support suppress higher order transverse spatial modes. The inventive optical resonator forces Higher higher order transverse modes to be fundamentally unstable in the inventive optical resonator, ultimately achieving ultimately to achieving single transverse mode resonator operation. Specifically, the bounded phase deflection mirror shape or intracavity lens profile is tailored to confine the fundamental mode while rendering the higher order modes unstable. This has application in MEMS/MOEMS optical resonator devices by suppressing the side modes and increasing the side mode suppression ratio (SMSR), as well as improving SMSR tolerance to device external alignment, for example. This also has application to achieving single transverse mode operation in laser resonators, such as in semiconductor vertical-cavity surface-emitting lasers (VCSEL).