A low-loss LNOI edge coupler fabricated on 4-inch wafer with deep ultraviolet lithography was demonstrated. The coupler was fabricated on LNOI with 600 nm thin-film lithium-niobate by 180nm lithography and ICP etch process. The 600nm thin-film lithium-niobate was etched for three times to achieve the coupler with tri-layer structure and narrow taper tips of below 150 nm. The fiber to chip coupling loss is 0.84 dB and 1.3 dB per facet for TE light at 1550 nm, when coupled with lensed fibers, which have 4 μm and 3.5 μm mode field diameter, respectively. Furthermore, the coupling loss is less than 1 dB per facet in the wavelength range between 1520 to 1560 nm.
One of the key challenges for realizing large-scale quantum communication in installed fiber networks is to establish communication links between multiple users in a scalable and robust way. Quantum networks based on DWDM quantum correlation utilizing broadband entangled photon pair source could be the solution. Among many integrated photon source techniques, AlGaAs Bragg reflection waveguid (BRW), with its extremely high material χ(2) and negligible birefringence, can produce high brightness, wide bandwidth, post selection free polarization entangled photon pairs. In a scenario of entangled photon and classical light co-fiber transmitting, noise from the classical light could degrade the entanglement. In this paper. we designed and fabricated a Bragg reflection waveguide (BRW) AlGaAs/GaAs chip with high modal overlap to directly generate broadband polarization entanglement, and employed for demonstrate a fully connected three-user noisy network by multiplexing 3 pairings of DWMD channels, each pairing established a quantum communication link between any possible two users. Several causes of noise from chip fluorescence to co-fiber classical light, and their impacts on bit error rate (BER) were analyzed.
The responsivity and the bandwidth are both key parameters of a PD but also encounter tradeoff during the device designing due to the thickness of InGaAs layer absorbing light. In this paper, a balanced structure to achieve both high speed and relatively high responsivity is reported. A uni-traveling carrier PD(UTC-PD) structure is taking advantage of the high drift velocity to meet the rather high-speed exhibition. For responsivity enhancing, we apply back reflector beneath the top-illuminated UTC-PD based on micro transfer printing. To further increase the bandwidth of small size PD, we optimize the shape of CPW electrodes of PDs. With our final structure, the UTC-PD exhibits 3dB bandwidth of 100GHz and responsivity of 0.4A/W.
As one of the most promising optical nonlinear material, AlGaAs has several advantages such as high second and third order nonlinear coefficients, freedom of material engineering, potential of full quantum photonic system on chip (SOC) including pump laser. In this paper, we estimate the photon pair generation and second harmonic generation (SHG) by an AlGaAs Bragg Rreflection waveguide (BRW) which design and manufactured on GaAs substrate.
GaAs Schottky barrier diode (SBD) based terahertz mixer and frequency multiplier represent one of the most important method for terahertz signal emitting and receiving from 0.5THz to 5THz. Compared with original GaAs substrate, quartz using as GaAs SBD circuit base could suppress transmission loss and high order transmission mode on chip, benefits from low dielectric constant of quartz. In this paper, GaAs SBD was integrated on quartz substrate using transfer printing technique, which could achieve membrane device transfer and low cost high output of original GaAs wafer.
The recently emerged photonic integration technology based on thin-film lithium niobate (LN) have been regarded as a very promising candidate for advanced photonic integrated circuits (PICs) due to its attractive nonlinear properties, wide-spread use in electro-optic applications, and etc. Generally, the thin-film LN optical waveguide used in PICs is sub-micrometer scale. Mode mismatch between fiber and sub-micrometer LN waveguide in chip is the main factor of increasing the fiber-to-chip coupling loss and the total insertion loss of LN PICs. Therefore, for practical applications, low-loss mode size converter for coupling between fiber and sub-micrometer LN waveguide is essential. In this paper, an efficient and novel fiber-to-chip mode size converter for thin-film LN PICs was designed and fabricated. The converter consists of a LN nano-taper and a cantilevered SiO2 waveguide. The nano-taper is embedded in the center of SiO2 waveguide. Laterally connected SiO2 cantilever beams are fabricated to provide structural support for the cantilevered SiO2 waveguide. Our work provides an efficient way to realize low-loss fiber-to-chip interface for thin-film LN PICs.
High performance optical transmitter with large bandwidth and high output power is one of the most important device in optical communications, 5th generation wireless systems and microwave photonics. We demonstrated an optical transmitter consisting of an InP-based large bandwidth travelling wave electrode (TWE) Mach-Zehnder electro-optic (EO) modulator hybrid integration with a high power distributed feedback (DFB) laser. The hybrid integration scheme was carefully designed. By using waveguide end-face coupling, the light from the InP-based DFB laser was effectively coupled into the input port of the Mach-Zehnder electro-optic modulator. A bright optical pattern at the output port of the EO modulator was observed. The output power of the integrated transmitter was measured about 0.27 mW with an inject current of 250 mA at room temperature. The transmission performance of high frequency signal was also verified by applying a microwave signal of 33 GHz. The results indicate that the simple and effective solution for hybrid integration of laser and EO modulator has potential applications in high speed optical communications.
A silicon hybrid photodetector was demonstrated based on die-to-die bonding technology. The vertically incident InGaAs/InP photodetector die was integrated on silicon-on-insulator (SOI) die by using divinyldisiloxane benzocyclobutene (DVS-BCB) as adhesive layer. A grating coupler was fabricated on SOI substrate to diffract the light out of the SOI waveguide into the detector. The measured coupling efficiency output at 1550 nm for the TE mode reached to 39.8%, which is equal to 8.2 dB fiber-to-fiber loss. After integrating, when the thickness of the BCB bonding layer was 380 nm, the optical loss reached to 13.8 dB with 30×30 μm2 device. The measured dark current, bandwidth and responsivity of the hybrid InGaAs/InP photodetector with light absorbing mesa of 10×10 μm2 were 37.7 nA, 30.9 GHz and 0.48 A/W respectively at -3 V DC bias.
Ultro-thin benzocyclobutene(BCB)bonding process has been proposed as a solution of InGaAs/Si optoelectronic heterogeneous integration. Here, we present a process of InGaAs PIN photodetector bonding onto silicon photonic chip, an ultra-thin bonding layer below 400nm is applied. Silicon photonic chip was fabricated by CMOS compatible process. In order to importing and exporting the light, a focal grating coupler was designed and fabricated, and fiber-to-chip efficiency was 37.7%. InGaAs PIN photodetector responsivity was 0.95A/W which taped out on 3 inch standard InP process. The result presented that the responsivity deterioration coefficient was below 1dB, and the coupling efficiency from Si waveguide to InGaAs photodetector was 41.8%.
We experimentally demonstrate high-speed InGaAs/InP drift-enhanced photodetectors with different diameters and absorbing layer thicknesses. For photodiodes with optical window diameters of 10 μm, 7 μm and 5 μm, we have achieved 3-dB bandwidths of 32GHz, 40 GHz and over 40 GHz from a 500-nm-thickness intrinsic InGaAs absorption layer and 30 GHz, 34 GHz and 36 GHz bandwidths from a 700-nm-thickness absorption layer, respectively. The measured values are in good agreement with the theoretical calculations.
A flat band-pass photonic filter is experimentally demonstrated on a silicon-on-insulator (SOI) substrate. The filter is composed of a micro-ring resonator assisted with an asymmetric Mach-Zehnder interferometer (MZI). By thermal tuning the ring, the device achieves a rapid roll-off on the band edges, a wide 3-dB bandwidth of 0.95 nm and a low crosstalk of 14 dB. The filter can be used in the WDM network and integrated microwave photonic signal processing.
A heterogeneous photonic integration of silicon photonic devices and III-V compound semiconductor photodetector (PD) is demonstrated by micro transfer printing (μ-TP). Via transfer printing, InP/InGaAs PIN PD is directly bonded on the top of silicon grating coupler by ultra-thin DVS-BCB adhesion layer. 0.4A/W of photo-responsibility @1550nm and ~25GHz of -3dB bandwidth are measured on printed PD. No deterioration in coupling loss is detected in the printed PD on the silicon gratings coupler with alignment accuracy of ±1μm. This technique enables a feasible route to photonic integrated circuits.
We have demonstrated a class of drift-enhanced InGaAs/InP p-i-n photodetectors with the top-illuminated light in the 1550 nm wavelength band. An InGaAsP layer is used at the InGaAs/InP hetero-interface to reduce the contact resistivity. For devices of 10 μm × 10 μm, 20 μm × 20 μm and 30 μm × 30 μm mesa areas, the 3-dB bandwidths are measured to be 32 GHz, 12 GHz and 6 GHz, respectively. Also we have obtained a dark current of 64 nA and a responsivity of 0.43 A/W at -4 V bias for 10 μm × 10 μm photodetector.
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