The enhanced transmission through periodic arrays of sub-wavelength holes in optically-thick metallic films has many potential applications, such as in wavelength filters, light extraction from light emission diodes, and subwavelength photolithography. A color filter comprising arrays of subwavelength holes in an aluminum film has been fabricated. In addition to the simplicity of the process, the aluminum film enables the excitation of visible-range surface plasmons due to its high plasma frequency. Periodic nanostructures in the aluminum film open the way for new visible color filters.
We demonstrated a novel two-dimensional photonic crystal (PC) based Symmetric Mach Zehnder type all-optical switch (PC-SMZ) with InAs quantum dots (QDs) acting as a nonlinear phase-shift source. The 600- ?m-long PC-SMZ having integrated wavelength-selective PC-based directional couplers and other PC components exhibited a 15-ps-wide switching-window with 2-ps rise/fall time at a wavelength of 1.3 ?m. Nonlinear optical phase shift in the 500-?m-long straight PC waveguide was also achieved at sufficiently low optical-energy (e.g., ??phase shift at ~100-fJ control-pulse energy) due to the small saturation energy density of the QDs, which is enhanced in the PC waveguide, without using conventional measures such as SOAs with current-injected gain. The results pave the way to novel PC- and QD-based photonic integrated circuits including multiple PC-SMZs and other novel functional devices.
We present the experimental realization of nanofiber Bragg grating (NFBG) by drilling periodic nano-grooves on a subwavelength-diameter silica fiber using focused ion beam milling technique. Using such NFBG structures we have realized nanofiber cavity systems. The typical finesse of such nanofiber cavity is F ∼ 20 - 120 and the on-resonance transmission is ∼ 30 - 80%. Moreover the structural symmetry of such NFBGs results in polarization-selective modes in the nanofiber cavity. Due to the strong confinement of the field in the guided mode, such a nanofiber cavity can become a promising workbench for cavity QED.
Polarization- and angle-independent, dual-band metasurface thermal emitter was developed. The metasurface emits radiation at 4.26 μm and 3.95 μm, conventionally used for CO2 sensing. The metasurface is based on a planar Au/Al2O3/Au structure, in which orthogonal rectangular Au patches are arrayed alternately, and generates nearly perfect blackbody radiation with an emittance as high as 0.97. The metasurface is integrated on a resistive heater mounted on a SiN membrane, so that the infrared waves are produced by applying a voltage. The metasurface emitter was incorporated into an actual CO2 sensing system and was demonstrated to reduce the electric power needed by about 30% compared with a conventional blackbody emitter by suppressing unnecessary radiation.
We have studied the dispersion of ultrafast pulses in a photonic crystal waveguide as a function of optical frequency, in both experiment and theory. With phase-sensitive and time-resolved near-field microscopy, the light was probed inside the waveguide in a non-invasive manner. The effect of dispersion on the shape of the pulses was determined. As the optical frequency decreased, the group velocity decreased. Simultaneously, the measured pulses were broadened during propagation, due to an increase in group velocity dispersion. On top of that, the pulses exhibited a strong asymmetric distortion as the propagation distance increased. The asymmetry increased as the group velocity decreased. The asymmetry of the pulses is caused by a strong increase of higher order dispersion. As the group velocity was reduced to 0.116(9) .c, we found group velocity dispersion of -1.1(3) .10(6) ps(2)/km and third order dispersion of up to 1.1(4) .10(5) ps(3)/km. We have modelled our interferometric measurements and included the full dispersion of the photonic crystal waveguide. Our mathematical model and the experimental findings showed a good correspondence. Our findings show that if the most commonly used slow light regime in photonic crystals is to be exploited, great care has to be taken about higher-order dispersion.
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