Research On Key Technology Of Light Beam Collimation With Lensed Fiber

Miniaturization and integration of optical system has become a new trend in recentyears. Fabricating micro lens on fiber end-face has become a new method to minimizeoptical systems. This method is widely used for medical instruments, biosciencetechnology, and communication technology and so on. To investigate the light beamcollimation with lensed fiber, theoretical research and experimental study have beencarried out as followed in this paper.1. Theoretical research on different fiber ends including axicon lensed fiber, Fresnelzone on fiber end-face, circle slit on fiber end-face and graded refractive index fiber(GRIN) was carried out. Derivation based on wave theory was used to analyze the lightpropagation.Simulation was run to investigate the light distribution in far field. Lightdistribution along the optical axis was simulated for each micro lens on fiber ends.Comparison was made among different fiber ends.2. A fiber polishing system was designed and assembled to fabricate the microaxicon on the fiber end. A micro axicon with a base angle of45°was fabricated on fiberend. Test results indicated that an axicon with a base angle of30°to45°could befabricated on fiber end with this fiber polishing system.3. Experiments were run to verify the characteristic of emission light in far field.Experiment results indicated that the stability was improved by45times by using axiconon fiber end. The axicon on fiber end reduced the divergence angle to11%of the lightcoming out from a flat fiber end. Divergence angle of light coming out from GRIN fiberswere1.63°to3.2°as the length of GRIN changed. This indicated that GRIN fibers couldreduce the divergence angle to39%compared to the flat fiber end. At30μm-50μm faraway from the micro lensed fiber end, the light spot had a high uniformity in intensityalong the radical axis.Experiments on divergence angle of light passed through GRINfibers with different length were run to investigate the relation between the collimationeffect and its length. Experiment results indicated that the relation between thecollimation effect by GRIN fiber and its length could be approximately considered assine function.4. Experiments were run to verify the resolution of these upgraded SCPs.Experiment results indicated that a resolution of20nanometers could be achievedcompared to the resolution of30nm in the past. It therefore could be concluded that byusing proposed lensed fiber in this paper the resolution of SCP was improved by33%。...