Jee Soo Chang

Label-free optical biosensing using a horizontal air-slot SiNx microdisk resonator.

We demonstrate label-free optical biosensing using a horizontal air-slotted silicon-rich silicon nitride (SiNx) microdisk resonator. Due to the strong confinement of light in the air-slot, a large resonance shift of 6.2 nm is observed upon reaction of the biotin-functionalized disk with a streptavidin solution with concentration of 2.5 μg/ml. Assuming a linear relationship between resonance shift and streptavidin concentration, we estimate the sensitivity to be 2.5 ± 0.2 nm/(μg/ml). Comparing this value with surface sensitivity of 5.7 nm/nm calculated using FDTD simulations, a detection limit of 30 ± 2 ng/ml, is extrapolated.

Cooperative upconversion and optical gain in ion-beam sputter-deposited Er x Y 2-x SiO 5 waveguides

Single-phase, polycrystalline Er(x)Y(2-x)SiO(5) thin films were deposited by reactive ion-beam sputter deposition and rapid thermal annealing. Due to the crystalline nature, the silicate thin films provide peak Er(3+) emission cross-section of 0.9 +/- 0.02 x 10(-20) cm(2) that is higher than that in silica. Optical gain, with near 60% inversion, is achieved via optical pumping of a single-mode, ridge-type waveguide with the silicate core with an Er concentration of 1.7 x 10(20) cm(-3). Analysis of pump-power dependence of the optical gain and spontaneous emission intensity of Er(3+) indicate that the gain is limited by cooperative upconversion process, whose coefficient is determined to be (8 +/- 3) x 10(-17) cm(3)/sec.

A silicon nitride microdisk resonator with a 40-nm-thin horizontal air slot

We design and fabricate pedestal-type, 15 microm diameter silicon nitride microdisk resonators on Si chip with horizontal air-slot using selective wet etching between Si, SiO2, and SiNx. As the slot structure is determined by deposition process, air slots that are as thin as 40 nm and as deep as 5 microm with ultra-smooth slot surfaces can easily be fabricated with photolithography only. Fundamental TM-like slot mode in which the E-field is greatly enhanced within slot was observed with an intrinsic Q factor of approximately 34,000 (lambdares=1523.7 nm) and energy overlap in slot region of 21.6%.

Si nanocluster sensitization of Er-doped silica for optical amplet using top-pumping visible LEDs

A review is presented of Si nanocluster sensitization of Er-doped silica for planar optical amplifiers using top-pumping 470-nm light-emitting diodes (LEDs). The motivation and basic physical principles underlying the nanocluster sensitization are first reviewed. The material structures necessary for optimum performances are presented, with emphasis on the need for nanoscale engineering of the composition and structure. Evidence of optical gain using commercial GaN-visible LEDs are presented, and the simulation results of possible device performances described. Finally, some possible future directions for research are discussed

Population inversion and low cooperative upconversion in Er-doped silicon-rich silicon nitride waveguide

Single-mode, strip-loaded silicon-rich silicon nitride (SRSN) waveguide with 11 at.% excess Si and 1.7×10(20) cm(-3) Er was fabricated and characterized. By using a 350 nm thick SRSN:Er core layer and a 850 nm wide SiO2 strip, a high core-mode overlap of 0.85 and low transmission loss of 2.9 dB/cm is achieved. Population inversion of 0.73-0.75, close to the theoretical maximum, is estimated to have been achieved via 1480 nm resonant pumping, indicating that nearly all doped Er in SRSN are optically active. Analysis of the pump power dependence of Er3+ luminescence intensity and lifetime indicate that the Er cooperative upconversion coefficient in SRSN:Er is as low as 2.1×10(-18) cm3/sec.

Fabrication and characterization of Er doped silicon-rich silicon nitride(SRSN) micro-disks

Micro-disk resonators were fabricated using Er doped silicon-rich silicon nitride (SRSN:Er). SRSN:Er thin films are fully CMOS-compatible and show efficient Er3+ luminescence pumped off-resonantly via Si nanoclusters. The high refractive index of SRSN (>2.0 at 1.5 μm) allows freedom in designing compact micro-disk resonators. Micro-disks with two different contents of Er (0.2 at.%, 0.02 at.%) with a diameter of 25 μm were fabricated, and characterized using evanescent coupling using tapered fibers. Whispering gallery modes with Q-factors in excess of 13000 were obtained, and FDTD calculations indicate that much higher values should be possible. Finally, we demonstrate excitation of fundamental whispering gallery mode via off-resonant, top-pumping of the SRSN microdisk.

Development and Application of Er-Doped Silicon-Rich Silicon Nitrides and Er Silicates for On-Chip Light Sources

On-chip light sources are a critical part for an integrated Si photonic technology, yet they lag other photonic components in their level of development. In this chapter, Er used as an optical dopant and utilizing its intra-4f transition at 1.54µm will be introduced as a viable means for on-chip light generation that has the advantage of being compatible with long-distance telecom as well. First, a general introduction to the topic of developing a Si-based/compatible light source will be presented, with emphasis on the need for a novel high-index material for Er-doping that can provide both a higher Er content and refractive index than has been reported so far. Second, Er-doped silicon-rich silicon nitride (SRSN) and Er silicates will be introduced as a promising host material for compact on-chip light sources. Finally, results of fabricating basic photonic components using Er-doped SRSN and Er-silicates will be presented.

Optical activity and population inversion of Er doped in silicon-rich silicon nitride

Optical activity and population inversion of Er doped in silicon-rich silicon nitride (SRSN) is investigated. Transmission measurements of SRSN waveguide shows that nearly all of doped Er is optically active even after high temperature anneals.

Optical biosensing using horizontal slot microdisk resonator

Biosensor using a horizontal slot microdisk resonator as a biosensor is demonstrated. Surface sensitivity of as high as 5.55 nm/nm is expected, and more than 9 nm shift upon sensing is demonstrated.

All planar integration of high-Q, Er-doped silicon-rich silicon nitride microdisk with SU-8 waveguide for on-chip, Si-based light source

All-planar integration of a light source with coupling waveguide on a Si chip is achieved using high-Q, Er doped silicon-rich silicon nitride (SRSN) microdisks and SU-8 waveguide. As-fabricated microdisks show Q-factors of 1–1.5×104 for both TE- and TM-like modes. Upon integration with single-mode SU-8 waveguide and clad with a polymer layer, Q-factor decreases to 5,000 for the TE-like mode, and 1,000 for TM-like mode. We obtain sharp Er3+ WGM emission coupled into the waveguide when the disk is pumped 1470 nm LD, indicating the promise of SRN:Er for compact, integrated Si- based light source.