This study investigates the influence of controlled mechanical strain on the wavelength characteristics of Vertical- Cavity Surface-Emitting Lasers (VCSELs), crucial components in optoelectronics, particularly in data centers. Using a custom four-point bending module, we systematically analyze the impact of strain on VCSELs by examining the wavelength evolution under varying strain levels. we report a consistent blue shift in the laser’s wavelength with increasing strain while maintaining stable power output. These findings highlight the potential of strain manipulation as a reliable technique for wavelength tuning in VCSELs, offering prospects for enhancing their performance in optical communication applications.
In this paper, we discuss 3 examples in which microlenses can be a useful tool to address challenges in coupling between a fiber array and photonic integrated circuit (PIC). The (arrays of) microlenses used in this work were realized by the photoresist reflow method and can either be monolithically integrated on the back side of a PIC or separately fabricated microlens blocks can be mounted on the device side of a PIC. The first example involves the implementation of silicon microlenses etched at the back side of a sensing PIC (operating in C-band) aiming at relaxed alignment tolerances and keeping the device side free of interfacing fibers. The second example involves the implementation of a 4-mm long working distance expanded beam (30 μm mode field diameter, C-band) interface for telecom/datacom applications which also greatly relaxes lateral and longitudinal alignment tolerances between grating couplers on PIC and a fiber array. The final example involves the integration of an isolator in this long working distance expanded beam interface. The isolator stack consisted of a polarizer (0.55 mm thick), a non-reciprocal Faraday Rotator (485 μm thick film latching Faraday Rotator) and half-wave plate (HWP, 91 μm quartz) glued on top of each other. We obtained broadband operation exhibiting a very low (between 1 and 1.5 dB) insertion loss and good extinction ratio (between 17 and 20 dB) in C-band (around 1550 nm).
We give an overview of our recent progress on the design and proof-of-concept demonstration of interfacing components for short-distance optical interconnects with a particular emphasis on their fabrication through two-photon polymerization-based laser direct writing. We show mode field conversion tapers printed on single-mode optical fibers for easy and efficient interfacing to various photonic integrated circuits, circular and square planar waveguide structures with V-groove inspired alignment structures for easy coupling to fibers, microlenses and fan-out diffractive optical elements.
We present the design, fabrication, and characterization cycle of a diffractive optical element based layout, used for 1-to-7 power splitting of a Gaussian beam emitted by a single-mode fiber. First, a modified version of our earlier demonstrated mode conversion up-taper structure is designed, fabricated, and characterized, increasing the mode-field diameter of the fundamental mode by a factor of 2. Then, a newly designed diffractive optical element is optimized to convert the expanded field distribution to a seven Gaussian-spot hexagonal array with 45 μm spacing, at an optimal propagation distance of only 61 μm, achieving splitting in a non-paraxial diffraction regime. The two components are combined into a monolithic design encompassing both adiabatic field expansion and efficient phase modulation in a single, highly miniaturized component. The power splitter is fabricated directly on the cleaved facet of a single-mode fiber, in a single step, using direct laser writing based on twophoton polymerization. The small spatial extent of the power splitter allows for a highly compact, integrated solution for wide-angle, fan-out power splitting of a Gaussian beam in single-mode interconnect and sensing applications.
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