Data are presented characterizing a new process for fabrication of vertical‐cavity surface‐emitting lasers based on the selective conversion of high Al composition epitaxial AlGaAs to a stable native oxide using ‘‘wet oxidation.’’ The native oxide is used to form a ring contact to the laser active region. The resulting laser active regions have dimensions of 8, 4, and 2 μm. The lowest threshold laser is achieved with the 8‐μm active region, with a minimum threshold current of 225‐μA continuous wave at room temperature.

Native-Oxide Defined Ring Contact for Low Threshold Vertical-Cavity Lasers

We address the long-standing issue of extracting light as efficiently as possible from a high-index material, n/spl ges/2, where as little as 2%-10% of light not suffering total internal reflection is extracted at standard plane faces due to the small critical angle /spl sim/1/n. Using a planar microcavity to redirect spontaneous emission toward the surface, constructive interferences can bring 15%-50% of the light out, enhancing brightness and efficiency. In this first of two papers, an approximate approach is used showing the importance of small cavity order m/sub c/ and of the m/sub c//n/sup 2/ ratio. We define a condition for microcavity regime as m/sub c/<2n/sup 2/. It is shown that most of light extraction is usually attained for moderate mirror reflectivities /spl sim/1-m/sub c//n/sup 2/ typically below 90%, and without strong directionality. Balance between emission directionality, radiance (brightness), and spectral narrowing is discussed. We define a brightness enhancement factor B given by Bm/sub c//spl Delta//spl Omega/=4/spl pi/ where /spl Delta//spl Omega/ is the largest internal solid angle of either the cavity mode or that deduced from the material emission linewidth. Design rules are applied to distributed dielectric mirrors yielding an optimal number of periods. The underlying physical competition between emission into guided modes, Fabry-Perot modes and the so-called "leaky modes" is analyzed.

/pdf/impact-of-planar-microcavity-effects-on-light-extraction-d0ycvxm6q4.pdf

Impact of planar microcavity effects on light extraction-Part I: basic concepts and analytical trends

Photonic integration on thinflexible plastic substrates is important for emerging applications ranging from the realization of flexible interconnects to conformal sensors applied to the skin. Such devices are traditionally fabricated using pattern transfer, which is complicated and has limited integration capacity. Here, we report a convenient monolithic approach to realize flexible, integrated high-index-contrast chalcogenide glass photonic devices. By developing local neutral axis designs and suitable fabrication techniques, we realize a suite of photonic devices including waveguides, microdisk resonators, add–drop filters and photonic crystals that have excellent optical performance and mechanical flexibility, enabling repeated bending down to sub-millimetre radii without measurable performance degradation. The approach offers a facile fabrication route for three-dimensional high-index-contrast photonics that are difficult to create using traditional methods.

Integrated flexible chalcogenide glass photonic devices

Chip-scale atomic devices combine elements of precision atomic spectroscopy, silicon micromachining, and advanced diode laser technology to create compact, low-power, and manufacturable instruments with high precision and stability. Microfabricated alkali vapor cells are at the heart of most of these technologies, and the fabrication of these cells is discussed in detail. We review the design, fabrication, and performance of chip-scale atomic clocks, magnetometers, and gyroscopes and discuss many applications in which these novel instruments are being used. Finally, we present prospects for future generations of miniaturized devices, such as photonically integrated systems and manufacturable devices, which may enable embedded absolute measurement of a broad range of physical quantities.

/pdf/chip-scale-atomic-devices-2t0mgeutgr.pdf

Chip-scale atomic devices

Vertical-cavity electrically driven lasers with three GaInAs
quantum wells and diameters of several μm exhibit room-temperature pulsed current thresholds as low as 1.3mA with 958 nm output wavelength.

Low-Threshold Electrically Pumps Vertical-Cavity Surface-Emitting Microlasers

We demonstrate a 300 μm long silicon photonic crystal (PC) slot waveguide device for on-chip near-infrared absorption spectroscopy, based on the Beer–Lambert law for the detection of methane gas. The device combines slow light in a PC waveguide with high electric field intensity in a low-index 90 nm wide slot, which effectively increases the optical absorption path length. A methane concentration of 100 ppm (parts per million) in nitrogen was measured.

http://chen-server.mer.utexas.edu/2011/sean011.pdf

On-chip methane sensing by near-IR absorption signatures in a photonic crystal slot waveguide

We design and fabricate a 320 nm slot for an electro-optic (E-O) polymer infiltrated silicon photonic crystal waveguide. Because of the large slot width, the poling efficiency of the infiltrated E-O polymer (AJCKL1/amorphous polycarbonate) is significantly improved. When coupled with the slow light effect from the silicon photonic crystal waveguide, an effective in-device r33 of 735 pm/V, which to our knowledge is a record high, is demonstrated, which is ten times higher than the E-O coefficient achieved in thin film material. Because of this ultrahigh E-O efficiency, the VπL of the device is only 0.44 V mm, which is to our knowledge the best result of all E-O polymer modulators.

Effective in-device r_33 of 735 pm/V on electro-optic polymer infiltrated silicon photonic crystal slot waveguides

We experimentally demonstrate a 300 μm long silicon photonic crystal slot waveguide near-infrared absorption spectrometer. Based on Beer–Lambert absorption law, our on-chip absorption spectrometer combines slow light in a photonic crystal waveguide with a high electric field intensity in a low-index 75 nm wide slot, which effectively increases the optical absorption path length of the analyte. We demonstrate near-infrared absorption spectroscopy of xylene in water, with a polydimethyl siloxane sensing phase for xylene extraction from water. Xylene concentrations up to 100 ppb (parts per billion) (86 μg/l) in water were measured.

/pdf/photonic-crystal-slot-waveguide-absorption-spectrometer-for-4efqpey3ei.pdf

Photonic crystal slot waveguide absorption spectrometer for on-chip near-infrared spectroscopy of xylene in water

In this paper, we present the design, fabrication, and characterization of a traveling-wave directional coupler modulator based on electro-optic polymer, which is able to provide both high linearity and broad bandwidth. The high linearity is realized by introducing Δβ -reversal technique in the two-domain directional coupler. A traveling-wave electrode is designed to function with bandwidth-length product of 302 GHz·cm , by achieving low microwave loss, excellent impedance matching, and velocity matching, as well as smooth electric-field profile transformation. The 3-dB bandwidth of the device is measured to be 10 GHz. The spurious-free dynamic range of 110 dB ±3 Hz2/3 is measured over the modulation frequency range of 2-8 GHz. To the best of our knowledge, such high linearity is first measured at the frequency up to 8 GHz. In addition, a 1 × 2 multimode interference 3-dB splitter, a photobleached refractive index taper, and a quasi-vertical taper are used to reduce the optical insertion loss of the device.

http://web.engr.oregonstate.edu/~wang/Documents/highly%20linear%20broadband%20optical%20modulator.pdf

Highly Linear Broadband Optical Modulator Based on Electro-Optic Polymer

We design a high dynamic range electric field sensor based on domain inverted electro-optic (E-O) polymer Y-fed directional coupler for electromagnetic wave detection. This electrode-less, all optical, wideband electrical field sensor is fabricated using standard processing for E-O polymer photonic devices. Experimental results demonstrate effective detection of electric field from 16.7V/m to 750KV/m at a frequency of 1GHz, and spurious free measurement range of 70dB.

/pdf/high-dynamic-range-electric-field-sensor-for-electromagnetic-1onm3d2rqa.pdf

Che-Yun Lin

Papers

On-chip methane sensing by near-IR absorption signatures in a photonic crystal slot waveguide

Effective in-device r_33 of 735 pm/V on electro-optic polymer infiltrated silicon photonic crystal slot waveguides

Photonic crystal slot waveguide absorption spectrometer for on-chip near-infrared spectroscopy of xylene in water

Highly Linear Broadband Optical Modulator Based on Electro-Optic Polymer

High dynamic range electric field sensor for electromagnetic pulse detection.