Research Terms
Optical Engineering Physical Sciences Optics Laser Physics
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The University of Central Florida invention provides a system for coherently combining laser amplifiers, including fiber and solid-state ones, to provide a coherent output laser beam using diffractive optical elements. For different applications, more laser power is required, and there are different means to achieve this. Some are based on combining lasers with different wavelengths, but some require the final laser beam to have a relatively narrow spectrum. To achieve this result, coherent beam combination is one approach. While separate laser resonators can be combined coherently, only a few attempts have been made to combine laser amplifiers. For the beam combining to be called "coherent" the light propagating through the amplifiers and consequently combined into a single beam should have the same phase and wavelength characteristics (central wavelength and spectral width). It basically behaves as though it was emitted from a single laser source.
As a solution, UCF researchers developed a technique for combining laser amplifiers and providing a robust source of coherent laser light. The high power from the combined outputs of laser amplifiers does not need additional phase control (active phase control) techniques.
Technical Details: In some embodiments, a laser source includes multiple laser amplifiers operating in parallel (for example, in different channels) between two nonpolarizing beamsplitters (the first and second nonpolarizing beamsplitters). The laser source may further include a seed laser source to generate a seed beam. This seed beam may be split by the first nonpolarizing beamsplitter into the multiple channels for a first pass of amplification, combined along a common path by the second beamsplitter, and retroreflected back to the second nonpolarizing beamsplitter by a Faraday mirror. The retroreflected light may then be split between the multiple channels by the second beamsplitter for a second pass of amplification and recombined by the first beamsplitter as a coherent output beam.
In other embodiments, the laser source can further include a polarizing beamsplitter between the seed laser and the first beamsplitter. In this way, the polarizing beamsplitter may pass linearly polarized seed light for amplification and direct the output beam along a separate path.
Partnering Opportunity: The research team is seeking partners for licensing, research collaboration, or both.
Researchers at the University of Central Florida have developed techniques for fabricating a new hybrid photonic element. Part of a novel class of hybrid grating, the UCF Phase-Shifted, Longitudinally Chirped Volume Bragg Grating (LCVBG) can be used to support tunable solid-state lasers with multiwavelength emission. The technology is capable of encoding phase information into both (1) the relative shift between local Bragg elements, and (2) the Bragg-period variation across the grating volume.
In the passive form, the phase-shifted, chirped VBG is a spectral beam shaper, wavelength-tunable across the transverse plane of its facet. The element is further doubled as a distributed feedback laser (DFB) when recorded into the optically active volume of doped photo-thermo-refractive (PTR) glass. The invention may also be used to create THz or GHz emitters for various applications.
Technical Details
In one application of the UCF invention, the example figure shows a phase-shifted, chirped VBG with a single notch axis, recorded in the optically active medium of doped PTR glass. In essence, it is a transversely chirped, distributed feedback laser (TCDFB). Packaged in a compact, monolithic volume of PTR glass, the grating element features an extended degree of resistance to high average- or peak-power laser radiation, mechanical shocks, and elevated temperatures.
End-pumped from one side by a laser diode with the emission wavelength tuned to around 981 nm, the active emitter matches the peak absorption of doped PTR glass. The monolithic source emits a pair of continuous-wave, single axial-mode laser beams near 1066 nm, from the element’s front and back facets. Analyzed by a scanning Fabry-Perot with 10 GHz of free spectral range, the axial-mode content at a diffracted output revealed the single-mode characteristic of coherent light being generated.
The versatile TCDFB element is a continuous collection of DFB sub-emitters, linearly distributed along the device’s end-facets. Due to the lack of cavity resonances, the change in emission wavelength is theorized to be continuous, mode-hop free over the entire tunable bandwidth—without the added complexity of phase-locking loops found in commercial devices. The rate of spectral tuning, though a fixed parameter, is adjustable during recording, as defined by the relative angle between the notch and chirp axes of the embedded grating.
Partnering Opportunity
The research team is looking for partners to develop the technology further for commercialization.
Stage of Development
Prototype available.
The University of Central Florida invention combines the principles of optical holography and Bragg diffraction to enable the complete reconstruction of a three-dimensional (3D) object. A conventional imaging system, typically found in a table-top microscope, captures the two-dimensional (2D) cross-section of a 3D space at a specific distance along its optical axis—the direction of illumination. Due to the restricted depth-of-field of such a platform, its operation is limited to imaging thin samples. For a thicker specimen, however, a stack of 2D cross-sections recorded at discrete points along its thickness is needed to reconstruct the object fully. The processing time of such an approach depends on the sample thickness, as well as the physical separation between consecutive cross-sections along the illumination direction (for example, the longitudinal resolution).
With an alternative approach to volumetric imaging, the invention obtains an image stack via a spectral sweep. As a result, the innovation enables a new type of 3D scanning microscope with no moving parts and the depth image acquisition is done by sweeping the wavelength of the light source. Applications include long-distance LIDAR depth sweeps and nano-surface profiles.
Partnering Opportunity
The research team is seeking partners for licensing and/or research collaboration.
Stage of Development
Prototype available.
