Abstract
We develop a method for synthesis of a desired intensity profile at the output of a multimode fiber (MMF) with random mode coupling by controlling the input field distribution using a spatial light modulator (SLM) whose complex reflectance is piecewise constant over a set of disjoint blocks. Depending on the application, the desired intensity profile may be known or unknown a priori. We pose the problem as optimization of an objective function quantifying, and derive a theoretical lower bound on the achievable objective function. We present an adaptive sequential coordinate ascent (SCA) algorithm for controlling the SLM, which does not require characterizing the full transfer characteristic of the MMF, and which converges to near the lower bound after one pass over the SLM blocks. This algorithm is faster than optimizations based on genetic algorithms or random assignment of SLM phases. We present simulated and experimental results applying the algorithm to forming spots of light at a MMF output, and describe how the algorithm can be applied to imaging.
Highlights
The ability to form a desired intensity profile at the output of a multimode fiber (MMF) has several promising applications, such as single-fiber scanning microscopy [1,2], optical coherence tomography [3], targeted light delivery [4], micromanipulation [5,6] and sensor multiplexing [7]
Assuming the desired intensity profile is known a priori, one approach is to use an spatial light modulator (SLM) to control the electric field at the MMF input, use a camera to monitor the intensity profile at the MMF output, and use an adaptive algorithm for finding the optimal SLM pattern
We model propagation of the electric field in the MMF by a random unitary propagation matrix U, which is a worst-case model for a real fiber, assuming negligible mode-dependent loss
Summary
The ability to form a desired intensity profile at the output of a MMF has several promising applications, such as single-fiber scanning microscopy [1,2], optical coherence tomography [3], targeted light delivery [4], micromanipulation [5,6] and sensor multiplexing [7]. The first class is based on measuring the entire electric field transmission matrix of a fiber or other scattering medium between each block of the SLM and each pixel of the camera [8,9,10]. Measuring this matrix requires approximately 4NSLM measurements, where NSLM is the number of SLM blocks. Once the transmission matrix has been measured, one can synthesize any number of desired field or intensity profiles at the MMF output
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
