Yigit O. Yilmaz

Optical channel dropping with a silicon microsphere

We report the observation of morphology-dependent resonances from silicon microspheres. The dropped channels are observed both in the transmission and elastic scattering spectra in the O-band. The filter drops approximately 23% of the power at the resonance wavelength. The highest observed quality factor for the morphology-dependent resonances was on the order of 10/sup 5/. These resonances have a linewidth of 0.007 nm and a mode spacing of 0.19 nm.

Fiber-optic beam shaper based on multimode interference

A new method of fiber-optic based beam shaping is investigated both numerically and experimentally. A cylindrically symmetric method of lines (MoLs) is developed to simulate the device. The device is fabricated by fusion splicing a predetermined length of multimode fiber (MMF) to a single-mode fiber. The multimode interference (MMI) effects create ring-shaped field profiles at certain positions inside the MMF. The shaped beam can be used in medical applications requiring particular irradiation patterns.

Spatial and spectral beam shaping with space-variant guided mode resonance filters

Novel all-dielectric beam shaping elements were developed based on guided mode resonance (GMR) filters. This was achieved by spatially varying the duty cycle of a hexagonal-cell GMR filter, to locally detune from the resonant condition, which resulted in modified wavelength dependent reflection and transmission profiles, across the device aperture. This paper presents the design, fabrication, and characterization of the device and compares simulations to experimental results.

Multiwavelength Blue Light Source Based on MgO : PPLN SHG Using Vertically Stacked Grating-Coupled Surface-Emitting Lasers

In this letter, we present the first experimental results of frequency doubling the output of vertically stacked grating coupled surface-emitting laser/dual-grating reflector devices with different emitting wavelengths. We used a multigrating 5% magnesium-oxide-doped periodically poled lithium niobate (MgO : PPLN) crystal as the nonlinear conversion medium. In pulse operation, 0.6 W of multiwavelength total second-harmonic peak power was obtained. The individual emitter output is focused into each channel of the crystal by diffractive beam shaping optical element array to minimize the footprint area of the whole setup.

Resonant channel-dropping filter with integrated detector system based on optical fiber coupler and microsphere

Dielectric microspheres are used to resonantly couple light from an optical fiber half coupler to a large-area silicon photodetector. Dielectric microspheres possess high quality factor morphology-dependent resonances, i.e., whispering gallery modes. The observed resonances have a channel spacing of 0.14 nm and a linewidth of 0.06 nm. These resonances provide the narrow linewidths necessary for high-resolution optical spectroscopy applications. Optical communication applications of this system are studied experimentally and theoretically.

Advanced fabrication methods for 3D meta-optics

Micro-Optics has expanded to include a wide variety of applications for spectral filtering, polarization filtering and beam shaping. Recently, a new class of optical elements have been introduced that can combine the spectral, polarization, and beam conditioning into the same optical element. This engineered optical functionality results in a 3D Meta-Optic structure that relies on sub-wavelength features to essentially engineer the electromagnetic fields within the structure; thereby, resulting in highly dispersive structures that spatially vary across the optical element. This talk will summarize recent results in the design, fabrication and applications of 3D Meta-Optics.

Micro-optical spatial and spectral elements

Interference filters have a defect layer incorporated within a photonic crystal structure and generate a narrow transmission notch within a wide stop band. In this paper, we propose and demonstrate wavelength-tunable spatial filters by introducing diffractive optical elements in the defect layer. The spectral transmission through the device was a function of the local defect layer thickness under broadband illumination. For each wavelength, the spatial transmission followed the contours of equal defect layer optical thickness. The devices were implemented by depositing a one-dimensional photonic crystal with a centrally integrated defect layer on a silicon substrate using plasma-enhanced chemical vapor deposition. The defect layer was lithographically patterned with charge 2, 8-level vortex structures. The spectral transmission peak and linewidth was characterized by separately illuminating each zone of diffractive element using a tunable laser source and compared with model simulations. The spatial transmission through the device was imaged onto a CCD camera. Triangular wedge-shaped zones with wavelength-dependent orientations were observed. These novel devices with spectrally tunable spatial transmission have potential applications in pupil filtering, hyperspectral imaging, and engineered illumination systems.

Blue Light Source Based on a ppKTP SHG Using a Grating-Coupled Laser Diode

In this letter, we present the first experimental results of a single-pass second-harmonic (SH) generation from a grating-coupled surface-emitting laser (GCSEL) with integrated dual-grating reflector. In pulse operation, the maximum SH peak power was obtained at 0.66 W, yielding a normalized conversion efficiency of 0.6times10-3 W-1. A high-level monolithical integration of the GCSEL device led to a compact blue light source, which was based on a frequency-doubled near-IR laser diode.

Blue light source based on spectrally stabilized external dual grating reflector coupled surface emitter array

Second harmonic generation (SHG) from near infrared (IR) diode lasers is an attractive solution for blue-light sources with high peak power and narrow linewidth. IR sources based on broad stripe devices with narrow linewidth makes it possible to achieve a wide range of wavelengths throughout the blue region. This paper summarizes recent results utilizing a configuration of external dual grating reflector coupled surface emitting laser array for blue light generation.

2-D Stacked External Cavity Multiwavelength Surface-Emitting Laser Array

In this letter, we present a multiwavelength two-dimensional array based on vertically stacked grating coupled surface-emitting laser bars. The emitters in the array were individually wavelength stabilized using external Littrow gratings fabricated on silicon-based spacers. In pulse operation, lasing with a ~0.3-nm linewidth from each device and maximum total peak power of 120 W was achieved.