Richard M. Osgood

Experimental Demonstration of Near-Infrared Negative-Index Metamaterials

Metal-based negative refractive-index materials have been extensively studied in the microwave region. However, negative-index metamaterials have not been realized at near-IR or visible frequencies due to difficulties of fabrication and to the generally poor optical properties of metals at these wavelengths. In this Letter, we report the first fabrication and experimental verification of a transversely structured metal-dielectric-metal multilayer exhibiting a negative refractive index around 2 microm. Both the amplitude and the phase of the transmission and reflection were measured experimentally, and are in good agreement with a rigorous coupled wave analysis.

Mid-infrared optical parametric amplifier using silicon nanophotonic waveguides

By taking advantage of the absorption reduction at wavelengths approaching the two-photon absorption bandedge of 2,200 nm, scientists demonstrate a mid-infrared silicon optical parametric amplifier that exhibits broadband gain as large as 25.4 dB and a net off-chip amplification of 13 dB using only an ultra-compact 4-mm silicon chip.

Near-infrared double negative metamaterials

We numerically demonstrate a metamaterial with both negative epsilon and negative mu over an overlapping near-infrared wavelength range resulting in a low loss negative-index material. Parametric studies optimizing this negative index are presented. This structure can be easily fabricated with standard semiconductor processing techniques.

Raman amplification in ultrasmall silicon-on-insulator wire waveguides.

We measure stimulated Raman gain at 1550 nm in an ultrasmall SOI strip waveguide, cross-section of 0.098 microm2. We obtain signal amplification of up to 0.7 dB in the counter-propagating configuration for a sample length of 4.2 mm and using a diode pump at 1435 nm with powers of <30 mW. The Raman amplifier has a figure-of-merit (FOM) of 57.47 dB/cm/W. This work shows the feasibility of ultrasmall SOI waveguides for the development of SOI-based on-chip optical amplifiers and active photonic integrated circuits.

Elliptical-hole photonic crystal fibers

We study the dispersive properties of photonic crystal fibers (PCFs) with elliptical air holes. The unusual guidance of PCF leads to novel behavior of the birefringence, group-velocity walk-off, and dispersion parameters, including the possibility of zero walk-off with high birefringence in the single-mode regime. A number of these effects are closely tied to the underlying radiation states of the air-hole lattice.

Fabrication of single-crystal lithium niobate films by crystal ion slicing

We report on the implementation of crystal ion slicing in lithium niobate (LiNbO3). Deep-ion implantation is used to create a buried sacrificial layer in single-crystal c-cut poled wafers of LiNbO3, inducing a large etch selectivity between the sacrificial layer and the rest of the sample. 9-μm-thick films of excellent quality are separated from the bulk and bonded to silicon and gallium arsenide substrates. These single-crystal films have the same room-temperature dielectric and pyroelectric characteristics, and ferroelectric transition temperature as single-crystal bulk. A stronger high-temperature pyroelectric response is found in the films.

C-band wavelength conversion in silicon photonic wire waveguides

We demonstrate C-band wavelength conversion in Si photonic-wire waveguides with submicron cross-section by means of nonresonant, nondegenerate four-wave mixing (FWM) using low-power, cw-laser sources. Our analysis shows that for these deeply scaled Si waveguides, FWM can be observed despite the large phase mismatch imposed by strong waveguide dispersion. The theoretical calculations agree well with proof-of-concept experiments. The nonresonant character of the FWM scheme employed allows to demonstrate frequency tuning of the idler from ~ 20 GHz to > 100 GHz thus covering several C-band DWDM channels.

Polarization and dispersive properties of elliptical-hole photonic crystal fibers

We survey the properties of photonic crystal fibers with elliptical air holes, examining mode shapes, birefringence, group velocity walkoff and dispersion, and cutoff conditions. We find new types of behavior for each quantity and demonstrate the possibility achieving large birefringence with zero walkoff in the single-mode regime. We show that the dispersive properties of the vector modes are closely tied to those of the so-called fundamental space filling modes, and that at long wavelengths, the fibers exhibit a single-polarization single-mode regime of propagation without the presence of material anisotropy.

Demonstration of metal-dielectric negative-index metamaterials with improved performance at optical frequencies

We experimentally demonstrate a comparatively low-loss negative-index metamaterial with the magnitude of the real part of the index comparable with the imaginary part. Over 40% transmission is achieved in the negative-index region by structural adjustment of the impedance matching between the metamaterial and the air-substrate claddings. This structure has the potential of achieving high transmission and small loss in the negative-index region.

Ultraviolet solid-state Ce:YLF laser at 325 nm

We describe the first reported observation of stimulated emission from a 5d-4f transition in a triply ionized rare-earth-doped crystal. Ce(+3) ions in LiYF(4) (YLF), optically pumped at 249 nm, emitted at 325.5 nm, the shortest wavelength yet obtained from an optically pumped solid-state laser. The large fluorescence linewidth of the laser transition makes the Ce:YLF laser a potentially tunable source of coherent near-ultraviolet radiation between 305 and 335 nm.