Ultrahigh-Q nanocavity with 1D photonic gap Notomi, M; Kuramochi, E; Taniyama, H
Optics express,
2008-Jul-21, 2008-07-21, 20080721, Letnik:
16, Številka:
15
Journal Article
Recenzirano
Odprti dostop
Recently, various wavelength-sized cavities with theoretical Q values of approximately 10(8) have been reported, however, they all employ 2D or 3D photonic band gaps to realize strong light ...confinement. Here we numerically demonstrate that ultrahigh-Q (2.0x10(8)) and wavelength-sized (V(eff) approximately 1.4(lambda/n)3) cavities can be achieved by employing only 1D periodicity.
This article overviews our recent studies of ultrahigh-Q and ultrasmall photonic-crystal cavities, and their applications to nonlinear optical processing and novel adiabatic control of light. First, ...we show our latest achievements of ultrahigh-Q photonic-crystal nanocavities, and present extreme slow-light demonstration. Next, we show all-optical bistable switching and memory operations based on enhanced optical nonlinearity in these nanocavities with extremely low power, and discuss their applicability for realizing chip-scale all-optical logic, such as flip-flop. Finally, we introduce adiabatic tuning of high-Q nanocavities, which leads to novel wavelength conversion and another type of optical memories.
The design, fabrication, and measurement of photonic-band-gap (PBG) waveguides, resonators and their coupled elements in two-dimensional photonic crystal (PhC) slabs have been investigated. We have ...studied various loss mechanisms in PBG waveguides and have achieved a very low propagation loss (~1 dB/mm). For these waveguides, we have observed a large group delay (>100 ps) by time-domain measurement. As regards PBG resonators, we realize very high-Q and small volume resonators in PhC slabs by appropriate design. Finally, we demonstrate various forms of coupled elements of waveguides and resonators: 2-port resonant-tunneling transmission devices, 4-port channel-drop devices using the slow light mode, and 3-port channel-drop devices using the resonant-tunneling process.
The introduction of the photonic crystal (PhC) wavelength-scale cavity as a laser cavity enables us to obtain both ultralow threshold current and operating energy. These parameters are essential when ...using the transmitters in chip-to-chip and on-chip interconnections. To improve the device performance, we employ an ultracompact embedded active region that we call a lambda-scale embedded active-region PhC laser or LEAP laser. We have developed an electrically driven LEAP laser, which operates under room-temperature continuous-wave conditions. To fabricate the electrically driven LEAP laser, we used Zn thermal diffusion and Si ion implantation, respectively, for p-type and n-type doping in an undoped InP layer. However, with previous fabricated devices there was a large leakage current through the substrate and the threshold current was 0.39 mA, which is larger than the expected threshold obtained by optical pumping. To reduce the leakage current, we propose using an InAlAs sacrificial laser instead of an InGaAs layer. The leakage current path through the substrate is effectively suppressed, and as a result, the threshold current is reduced to 7.8 μA, which is the lowest threshold current reported for any laser. Furthermore, the LEAP laser operates at up to 95 °C by using an InGaAlAs-based multiple quantum well structure. We also describe the dynamic characteristics of the laser. The LEAP laser exhibits a maximum 3-dB bandwidth of 16.2 GHz and the modulation current efficiency factor is 53.8 GHz/mA 0.5 or 1.7 GHz/μA 0.5 , which is four times that of a vertical cavity surface-emitting laser. The device is directly modulated by a 12.5-Gb/s nonreturn-to-zero signal with a bias voltage of 1.6 V and a bias current of 109 μA, resulting in an energy cost of 14.0 fJ/b. This is the smallest operating energy for any laser. These results indicate that the LEAP laser is highly suitable for use as a transmitter in computercom applications.
Carrier dynamics in silicon photonic crystal (PhC) nanocavities are studied numerically. The results agree well with previous experimental demonstrations. It is shown that the presence of carrier ...diffusion makes fast switching possible, which is an advantage of nanocavity switches over other types of larger carrier based nonlinear optical switches. In particular, diffusion is effective in PhC nanocavity switches, which makes the switching recovery time even faster than that of silicon waveguide-based optical switches. In addition, calculations suggest that the thermo-optic effect can be reduced if the carriers are extracted within a few 100 ps by introducing a p-i-n structure.
We investigate the inhibited spontaneous emission of telecom-band InAs quantum disks (Qdisks) in InP nanowires (NWs). We have evaluated how the inhibition is affected by different disk diameter and ...thickness. We also compared the inhibition in standing InP NWs and those NWs laying on silica (SiO(2)), and silicon (Si) substrates. We found that the inhibition is altered when we put the NW on the high-refractive-index materials of Si. Experimentally, the inhibition factor ζ of the Qdisk emission at 1,500 nm decreases from 4.6 to 2.5 for NW on SiO(2) and Si substrates, respectively. Those inhibitions are even much smaller than that of 6.4 of the standing NW. The inhibition factors well agree with those calculated from the coupling of the Qdisk to the fundamental guided mode and the continuum of radiative modes. Our observation can be useful for the integration of the NW as light sources in the photonic nanodevices.
We experimentally demonstrate the structural tuning of the waveguiding modes of line defects in photonic crystal (PC) slabs. By tuning the defect widths, we realized efficient single-mode waveguides ...that operate within photonic band gap frequencies in silicon-on-insulator PC slabs. The observed waveguiding characteristics agree very well with three-dimensional finite difference time-domain calculations. We also directly measured the propagation loss of the line defect waveguides and obtained a value of 6 dB/mm.
The superprism phenomenon, the dispersion of light 500 times stronger than the dispersion in conventional prisms, was demonstrated at optical wavelengths in photonic crystals (PC's) fabricated on Si. ...Drastic light-beam steering in the PC's was achieved by slightly changing the incident wavelength or angle. The scanning span reached 50/spl deg/ with only a 1% shift of incident wavelength, and reached 140/spl deg/ with only a 14/spl deg/ shift of the incident angle at wavelengths around 1 /spl mu/m. The propagation direction was quantitatively interpreted in terms of highly anisotropic dispersion surfaces derived by photonic band calculation. The physics behind this demonstration will open a novel field called photonic crystalline optics. The application of these phenomena promises to enable the fabrication of integrated microscale lightwave circuits (/spl mu/LC's) on Si with large scale integrated (LSI)-compatible lithography techniques. Such /spl mu/LC's will allow more efficient use of wavelength resources when used in wavelength multiplexers/demultiplexers or dispersion compensators by enabling lower loss and broader bandwidth.
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