Remote electric powering by germanium photovoltaic conversion of an Erbium-fiber laser beam

The commercially available 4000-Watt continuous-wave(CW)Erbium-doped-fiber laser,emitting at the 1567-nm wavelength where the atmosphere has high transmission,provides an opportunity for harvesting electric power at remote“off the grid”locations using a multi-module photovoltaic(PV)“receiver”panel.This paper proposes a 32-element monocrystalline thick-layer Germanium PV panel for efficient harvesting of a collimated 1.13-m-diam beam.The 0.78-m^(2) PV panel is constructed from commercial Ge wafers.For incident CW laser-beam power in the 4000 to 10,000 W range,our thermal,electrical,and infrared simulations predict 660 to 1510 Watts of electrical output at the panel temperatures of 350 to 423 K.

Electric-field-induced quasi-phase-matched three-wave mixing in silicon-based superlattice-on-insulator integrated circuits

We present a theoretical investigation,based on the tight-binding Hamiltonian,of efficient electric-field-induced three-waves mixing(EFIM)in an undoped lattice-matched short-period superlattice(SL)that integrates quasi-phase-matched(QPM)SL straight waveguides and SL racetrack resonators on an opto-electronic chip.Periodically reversed DC voltage is applied to electrode segments on each side of the strip waveguide.The spectra ofχ_(xxxx)^((3))and of the linear suscepti-bility have been simulated as a function of the number of the atomic monolayers for“non-relaxed”heterointerfaces,and by considering all the transitions between valence and conduction bands.The large ob-tained values ofχ_(xxxx)^((3))make the(ZnS)3/(Si2)3 short-period SL a good candidate for realizing large effective second-order nonlinearity,en-abling future high-performance of the SLOI PICs and OEICs in the 1000-nm and 2000-nm wavelengths ranges.We have made detailed calculations of the efficiency of second-harmonic generation and of the performances of the optical parametric oscillator(OPO).The re-sults indicate that the(ZnS)N/(Si2)M QPM is competitive with present PPLN technologies and is practical for classical and quantum appli-cations.

Compact, submilliwatt, 2 × 2 silicon thermo-optic switch based on photonic crystal nanobeam cavities

We propose and experimentally demonstrate a 2×2 thermo-optic(TO) crossbar switch implemented by dual photonic crystal nanobeam(PCN)cavities within a silicon-on-insulator(SOI)platform.By thermally tuning the refractive index of silicon,the resonance wavelength of the PCN cavities can be red-shifted.With the help of the ultrasmall mode volumes of the PCN cavities,only～0.16 mW power is needed to change the switching state.With a spectral passband of 0.09 nm at the 1583.75 nm operation wavelength,the insertion loss(IL)and crosstalk(CT)performances were measured as IL(bar)=-0.2 dB,CT(bar)=-15 dB,IL(cross)=-1.5 dB,and CT(cross)=-15 dB.Furthermore,the thermal tuning efficiency of the fabricated device is as high as1.23 nm/mW.

Mid-infrared 2×2 electro-optical switching by silicon and germanium three-waveguide and four-waveguide directional couplers using free-carrier injection

New designs are proposed for 2×2 electro-optical switching in the 1.3–12μm wavelength range.Directional couplers are analyzed using a two-dimensional effective-index approximation.It is shown that three or four side-coupled Si or Ge channel waveguides can provide complete crossbar broad-spectrum switching when the central waveguides are injected with electrons and holes to modify the waveguides’core index by an amountΔn+iΔk.The four-waveguide device is found to have a required active length L that is 50%shorter than L for the three-waveguide switch.A rule ofΔβL>28 for 3w andΔβL>14 for 4w is deduced to promise insertion loss<1.5 dB and crosstalk<−15 dB at the bar state.At an injection ofΔNe=ΔNh=5×10^(17)cm^(−3),the predicted L decreased from∼2 to∼0.5 mm asλincreased from 1.32 to 12μm.Because of Ge’s largeΔk,the Ge bar loss is high in 4w but is acceptable in 3w.

Design of low-energy on-chip electro-optical 1 × M wavelength-selective switches

A theoretical design is presented for a 1 × M wavelength-selective switch(WSS) that routes any one of N incoming wavelength signals to any one of M output ports. This planar on-chip device comprises of a 1 × N demultiplexer, a group of N switching "trees" actuated by electro-optical or thermo-optical means, and an M-fold set of N × 1multiplexers. Trees utilize 1 × 2 switches. The WSS insertion loss is proportional to [log_2(M+N +1)]. Along with cross talk from trees, cross talk is present at each cross-illuminated waveguide intersection within the WSS, and there are at most N-1 such crossings per path. These loss and cross talk properties will likely place a practical limit of N=M=16 upon the WSS size. By constraining the 1 × 2 switching energy to^1 f J∕bit, we find that resonant, narrowband 1 × 2 switches are required. The 1 × 2 devices proposed here are nanobeam Mach–Zehnders and asymmetric contra-directional couplers with grating assistance.

Classical and quantum photonic sources based upon a nonlinear GaP/Si-superlattice micro-ring resonator

We present a theoretical investigation,based on the tight-binding Hamiltonian,of efficient second-and third-order nonlinear optical processes in the lattice-matched undoped(GaP)N/(Si 2)M short-period superlattice that is waveguide-integrated in a microring resonator on an opto-electronic chip.The nonlinear superlattice structures are sit-uated on the optically pumped input area of a heterogeneous“XOI”chip based on silicon.The spectra ofχ(2)zzz(2ω,ω,ω),χ(2)xzx(2ω,ω,ω),χ(3)xxxx(3ω,ω,ω,ω)and the Kerr refractive index(n 2),have been simu-lated as a function of the number of the atomic monolayers for“non-relaxed”heterointerfaces;These nonlinearities are induced by transi-tions between valence and conduction bands.The large obtained val-ues make the(GaP)N/(Si 2)M short-period superlattice a good can-didate for future high-performance XOI photonic integrated chips that may include Si 3 N 4 or SiC or AlGaAs or Si.Near or at the 810-nm and 1550-nm wavelengths,we have made detailed calculations of the efficiency of second-and third-harmonic generation as well as the performances of entangled photon-pair quantum sources that are based upon spontaneous parametric down conversion and sponta-neous four-wave mixing.The results indicate that the(GaP)N/(Si 2)M short-period superlattice is competitive with present technologies and is practical for classical and quantum applications.