We present progress on our holographic adaptive laser optics system (HALOS): a compact, closed-loop aberration
correction system that uses a multiplexed hologram to deconvolve the phase aberrations in an input beam. The wavefront
characterization is based on simple, parallel measurements of the intensity of fixed focal spots and does not require any
complex calculations. As such, the system does not require a computer and is thus much cheaper, less complex than
conventional approaches. We present details of a fully functional, closed-loop prototype incorporating a 32-element
MEMS mirror, operating at a bandwidth of over 10kHz. Additionally, since the all-optical sensing is made in parallel,
the speed is independent of actuator number - running at the same bandwidth for one actuator as for a million.
We present a new method to lock an unlimited number of lasers using a simple, inexpensive hologram and photodiodes. Multiple fiber laser inputs are sent through a fiber shifters and then onto two holographic optical elements that split each beam in two and mix them in pairs. By taking the ratio of intensities measured from photodiodes, an error signal is generated which can be used to control the phase shifters to ensure continuous phase locking of pairs of lasers. We have constructed an autonomous system that locks 3 lasers and occupies a footprint no larger than a laptop. Locking is robust and can be configured to work with lasers of any power and wavelength. Our current system operates at bandwidths of up to 10kHz but has the potential of 100MHz or faster using a two-stage, woofer-tweeter approach.
We present an adaptive optics system which uses a multiplexed hologram to deconvolve the phase aberrations in an input beam. The wavefront characterization is extremely fast as it is based on simple measurements of the intensity of focal spots and does not require any complex calculations. Furthermore, the system does not require a computer in the loop and is thus much cheaper, more compact and more robust as well. A fully functional, closed-loop prototype incorporating a 32-element MEMS mirror has been constructed. The unit has a footprint no larger than a laptop but runs at bandwidths over an order of magnitude faster than comparable, conventional systems occupying a significantly larger volume. Additionally, since the sensing is based on parallel, all-optical processing, the speed is independent of actuator number – running at the same bandwidth for one actuator as for a million.
We have created a new autonomous (computer-free) adaptive optics system using holographic modal wavefront sensing and closed-loop control of a MEMS deformable mirror (DM). A multiplexed hologram is recorded using the maximum and minimum actuator positions on the deformable mirror as the "modes". On reconstruction, an input beam is diffracted into pairs of focal spots and the ratio of the intensities of certain pairs determines the absolute wavefront phase at a particular actuator location. We present the results from an ultra-compact, 32-actuator prototype device operating at 100 kHz. It is largely insensitive to obscuration and has a speed independent of the number of actuators.
The spatial-spectral holographic imaging system (S2-VHIS) is a promising alternative to confocal microscopy due to its capabilities to simultaneously image several sample depths with high resolution. However, the field of view of previously presented S2-VHIS prototypes has been restricted to less than 200 µm. We present experimental results of an improved S2-VHIS design that has a field of view of ~1 mm while maintaining high resolution and dynamic range.
Multiplexed gratings can be used in an imaging system to project depth sections of a tested object onto different surface
locations of a camera. This technique is based on volume holographic Bragg filters used in conjunction with
conventional optical imaging components to form a volume holographic imaging system (VHIS). Due to the high
angular selectivity and high wavelength selectivity of the system, the VHIS can be used to provide spectral-spatial
information of the object that is being observed, and eliminate the need for mechanical scanning. Multiple sections of
the object can be viewed by using angle multiplexed holographic elements formed in a volume holographic material. To
achieve the highly selective characteristic of a holographic filter, 2mm thick samples of phenanthrenequinone-doped
methyl methacrylate (PQ-PMMA) is used as the holographic recording materials. Rigorous coupled wave models are
used to theoretically predict the performance of the gratings. Results from both modeling and experiments are presented.