Tunable finesse optical filters and resonators are required for some applications when the signal-to-noise ratio and spectral resolution are traded-off to optimize the system performance. They can be used as well to control the amount of energy stored inside the resonator that can be used for optical trapping and atomistic studies. In this work we report a tunable finesse optical MEMS filter in deeply-etched SOI technology. The structure is composed of an optical cavity formed between a multilayer dielectric-coated optical fiber and slotted micromirror, attached to a comb-drive actuator. The cavity length between the multilayer Bragg coated fiber and the slotted micromirror is constant, while the slit width is being varied. The slit width is controlled by the applied voltage on the actuator. Changing the slit width modulates the reflectivity of the micromirror; and hence the finesse of the optical cavity. The obtained finesse is tuned by a factor of 5 across the band of 1330 nm and 1550 nm.
In this work we report a novel optical MEMS deeply-etched mirror with metallic coating and vertical slot, where the later allows reflection and transmission by the micromirror. The micromirror as well as fiber grooves are fabricated using deep reactive ion etching technology, where the optical axis is in-plane and the components are self-aligned. The etching depth is 150 μm chosen to improve the micromirror optical throughput. The vertical optical structure is Al metal coated using the shadow mask technique. A fiber-coupled Fabry-Pérot filter is successfully realized using the fabricated structure. Experimental measurements were obtained based on a dielectric-coated optical fiber inserted into a fiber groove facing the slotted micromirror. A versatile performance in terms of the free spectral range and 3-dB bandwidth is achieved.
We report a MEMS optical tunable filter based on high-aspect-ratio etching of sub-wavelength silicon layers on a silicon-
on-insulator wafer. The reported filter has measured free-spectral and filter-tuning ranges of approximately 100 nm
and a finesse of about 20 around a wavelength of 1550 nm, enabled by the use of 1000 nm-thick silicon layers and a balanced
tilt-free motion using a lithographically-aligned electrostatic actuator. The average insertion loss of the filter is
about 12 dB with a superior wavelength-dependent loss of about 1.5 dB. The filter has an out-of-band to in-band wavelength
rejection ratio that is better than 20 dB. The reported filter experimental characteristics and its integrability are
suitable for the production of integrated swept sources for optical coherence tomography application and miniaturized
In this work we study the effect of the ring width on the performance of a ring generated Bessel beam. Experimental
results and simulation model for ring generated Bessel beams are investigated and compared. The simulation model is
based on Fourier optics. The effect of varying the ring radius and the ring width on the Bessel beam parameters like the
axial intensity and the detected output power transported by the beam passing through the ring is studied. A good
agreement is found between the simulation model and the measurements. Larger ring width led to higher efficiency
(output power) but to less beam quality.