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The integration of BaTiO3 with Si(100) is essential to exploit its ferroelectric capabilities in the well-established Si-complementary metal–oxide–semiconductor (CMOS) technological platform. To en...

This work presents a wafer-scale two-step liquid phase crystallization process to obtain polycrystalline but epitaxial germanium on 2”-silicon wafers (Ge-on-Si). The crystallinity is confirmed using Raman spectroscopy and X-ray diffraction, with an extracted dislocation density of 108cm−2, an improvement of 10x over the previous report. The scanning electron imaging shows a uniform Ge film with a grain size of up to $12~\mu \text{m}$ . Metal-semiconductor-metal (MSM) near-infrared (IR) photodiodes are fabricated on the epitaxial Ge with two different electrodes and two different surface passivation interlayers. Irrespective of the electrode/passivation combination, all devices exhibit Ohmic characteristics. Contact resistivity varies from 3 $\text{m}\Omega $ cm2 to 560 $\text{m}\Omega $ cm2. This is contrary to virtually every previous report on MSM detector on n -type Ge . To probe further, kelvin probe force microscopy is used to characterize the surface potentials at grain boundaries and metal- Ge interfaces. The grain-to-grain band bending is very low, ~40 meV, hence, device characteristics are completely dominated by the metal- Ge band-bending which is 150–300 meV. The MSM devices using amorphous-Ge(30nm)/ Al (100nm) and TiO2 (5nm)/ Au (80nm) electrodes show an average spectral responsivity (SR) of 0.50 ± 0.16 A/W and 0.35 ± 0.09 A/W at 1550 nm and voltage bias of -3V, respectively. The maximum SR is 0.78 A/W and 0.48 A/W, respectively.

We present for the first time sputter deposition of PZT -on-SOl for electro-optic modulation. We present material, electric and electro-optic characteristics of a thin-film PZT -on-silicon. We demonstrate DC electro-optic characteristics using a ring resonator with a shift of 12.5 pm/V.

We demonstrate controlled phase tuning of thermal evaporated germanium antimony telluride (GST) integrated silicon ring resonator. The controlled cycling allows access to multi-states resulting in multi-photonic states for the potential neuromorphic application. We present and correlate electrical and photonic phase transition of ring integrated GST.

We design and experimentally demonstrate highly efficient Silicon Nitride based grating couplers with bottom distributed Bragg reflectors. All the layers were deposited using plasma enhanced chemical vapor deposition processing. We present gratings on two Silicon Nitride thickness (400 nm and 500 nm) platforms. On a 500 nm thick Silicon Nitride, we show a peak coupling efficiency of -2.29 dB/coupler at a wavelength of 1573 nm with a 1 dB bandwidth of 49 nm. On a 400 nm thick platform, we demonstrate a coupling efficiency of -2.58 dB/coupler at 1576 nm with a 1 dB bandwidth of 52 nm. The demonstrated coupling efficiency is the best reported as yet, for both 400 nm and 500 nm thick, plasma deposited Silicon Nitride platforms.

Thermo-optic effect is the simplest and most cost-effective method for reconfiguring an optical cavity, but fails to tune the optical loss in an ordinary cavity. By embedding an interferometer within an optical cavity, we demonstrate thermo-optic tuning of the quality factor from 3000 to 10000 and extinction ratio from ~0 dB to 25 dB in a completely passive silicon micro-ring resonator. This is an important step towards realizing cost-effective reconfigurable photonic devices in purely passive waveguide platforms.

We demonstrate 1X6 SiN echelle grating filters integrated with silicon nano-slab metal-semiconductor-metal photodetector for SWDM based short-reach interconnect. Echelle grating measures 4.3 dB insertion loss and 22 dB crosstalk. Photodetector records 0.59 A/W responsivity.

In this paper, we demonstrate controlled phase tuning of thermally evaporated germanium antimony telluride (GST) integrated silicon ring-resonator for potential neuromorphic application. We present and correlate electrical and photonic phase transition of ring integrated GST.

We demonstrate high-efficiency Silicon Nitride gratings for fiber-chip coupling in 850-900 nm. Experimentally measured peak efficiency is -4.44 dB and -3.4 dB for uniform and apodized gratings, respectively.

We present a compact on-chip resonator enhanced silicon metal-semiconductor-metal (MSM) photodetector in 850 nm wavelength band for communication and lab-on-chip bio-sensing applications. We report the highest responsivity of 0.81 A/W for a 5 µm long device. High responsivity is achieved by integrating the detector in a silicon nitride ring resonator. The resonance offers 100X responsivity improvement over a single-pass photodetector due to cavity enhancement. We also present a detailed study of the high-speed response of the cavity and single-pass detector. We report an electro-optic bandwidth of 7.5 GHz measured using a femtosecond optical excitation. To the best of our knowledge, we report for the first time silicon nitride resonator integrated Si-MSM detector in SiN-SOI platform.

On-chip spectroscopy in visible and near-infrared wavelength offers immense potential for various screening and diagnostic application. Silicon Nitride (SiN) is a promising material to realize on-chip spectroscopy as it is transparent over a broad wavelength spectrum; visible-to-mid-infrared. Besides, it is compatible with the CMOS process technology. Since SiN can be deposited using various deposition techniques, it is essential that an appropriate deposition process is chosen to achieve desired properties. We present a detailed study of SiN films deposited using PECVD and LPCVD process. The films were characterized for various, material and optical properties. We also performed waveguide transmission measurement on different SiN films and found a strong correlation with material properties such as stress and autofluorescence to achieve low-loss waveguide. Using the optimized material, we design, fabricate, and demonstrate single-mode SiN wire, spiral waveguides and grating fiber-chip coupler at visible (λ =520nm) and near infra-red (λ = 780nm) wavelengths used for spectroscopy. Furthermore, we use a waveguide to efficiently excite fluorescence or Raman active molecules drop casted as the top cladding of the waveguides. A fraction of the isotopically emitted fluorescence or Raman signal couples back to waveguide and rest is emitted normal to the surface. We discuss the theoretical efficiencies of both the methods of collection and compare it with the conventional microscope-based spectroscopic system. Waveguide based spectroscopic sensing offers higher efficiency due to increased light-matter interaction along the length of the waveguide. We presented detailed design, simulation, and experimental demonstration of grating coupler waveguide system suitable for son-chip spectroscopy application.

We experimentally demonstrated polarization independent, angle tolerant mid-infrared notch filters using amorphous-Germanium 2D high contrast gratings. Centered at 7.42 pm wavelength, the filter exhibits wide field-of-view notch filtering characteristics across 0 to 30o incidence angles.

We present a detailed experimental study of mitigation of two-photon absorption (TPA) in silicon microring modulator. In this work, we report the effect of optical and electrical signal power on the spectral characteristics of a ring modulator.

We demonstrate high efficiency grating couplers on Silicon Nitride in the C-L band region. The measured efficiency is -1.17 dB for 500 nm thick film and -1.24 dB for 400 nm thick film.

We present a multi-domain and orientation simulation study of thin-film Barium Titanate. We present the effect of domains on the effective index change under the electric field for unpoled and poled thin films.

An electro-optic device in silicon such as a photodetector and a modulator requires doping to realize desired junctions. Doping Si is typically done using ion-implantation or the thermal diffusion process. Both processes rely on high-temperature anneal to either activate or drive the dopant into the bulk. As diffusion of dopants is a thermally driven process, knowledge of actual diffusion lengths is essential for efficient device designs. Unlike other methods, we present an integrated-silicon-photonic-device-based lateral diffusion length characterization technique. A silicon microring resonator is used as a test device for the demonstration in a silicon-on-insulator substrate. Lateral diffusion lengths of 0.35 and $0.69~\mu \text{m}$ have been obtained for the drive-in temperatures of 950 °C and 1100 °C, respectively. We also present process simulation results to validate the experimental result.

We present a detailed study of electrical and optical generated free carrier on the spectral characteristics of a silicon microring modulator. The spectral distortion generated due to thermal and free carriers is presented, and the mechanism for mitigation is also presented. We observed that two-photon induced nonlinearity could be addressed by operating the modulator at suitable bias points. Furthermore, by applying small-signal drive the spectral distortion can be restored. We also present the effect of optical power and drive signal limit on the spectral characteristics. The study allows one to identify suitable device performance and operating conditions to utilize silicon ring modulator for optical signal processing.

Silicon Nitride (SiN) is emerging as a promising material for a variety of integrated photonic applications. Given its low index contrast however, a key challenge remains to design efficient couplers for the numerous platforms in SiN photonics portfolio. Using a combination of bottom reflector and a chirp generating algorithm, we propose and demonstrate high efficiency, grating couplers on two distinct SiN platforms. For a partially etched grating on 500 nm thick SiN, a calculated peak efficiency of −0.5 dB/coupler is predicted, while for a fully etched grating on 400 nm thick SiN, an efficiency of −0.4 dB/coupler is predicted. Experimentally measured coupling efficiencies are observed to be −1.17 and −1.24 dB/coupler for the partial and fully etched grating couplers respectively in the C-L band region. Furthermore, through numerical simulations, it is shown that the chirping algorithm can be implemented in eight additional combinations comprising SiN film thickness between 300–700 nm as well as alternate claddings, to achieve a per coupler loss between −0.33 to −0.65 dB.

We report and demonstrate high efficiency grating couplers on PECVD deposited Silicon Nitride films. The couplers were fabricated on a 400 nm thick film that was embedded in a SiO 2 cladding. The experimentally measured coupling efficiency was −5.6 dB per coupler for gratings on a Silicon substrate and −2.58 dB per coupler for gratings with a bottom Bragg reflector. The reported efficiencies are comparable to similarly deposited stacks using LPCVD based processes.

We demonstrate on-chip integrated, high-speed cavity-enhanced Silicon MSM photodetector on SiN-SOI platform for short-reach optical datacom at 850 nm wavelength. Silicon MSM photodetector is integrated inside a SiN ring resonator cavity. Compare to the conventional waveguide integrated photodetector the proposed device achieves 10X fold enhancement in responsivity at 850 nm wavelength. High-speed characterization of the proposed device is performed by capturing the impulse response of the device with illumination of femtosecond duration pulse laser at 850 nm wavelength. We measure 3dB bandwidth of 6.1 GHz which can be further be improved suitable for datacoms and supercomputers.

We present design and demonstration of visible light compatible silicon nitride waveguide and grating coupler for on-chip sensing applications.

We propose and demonstrate a versatile waveguide configuration that offers a widely tunable waveguide dispersion. The waveguide is formed by sandwiching high-index silicon between medium-index silicon nitride. We demonstrate grating couplers for both TE and TM mode with efficiency of -3.27 and -8 dB per coupler respectively and also demonstrate a ring resonator with a Q-factor of 3400 and a maximum extinction of 30 dB.

On-chip Optical Frequency Combs find use in a variety of applications: Chipscale precision metrology, sensing, in high-speed optical communications as Wavelength Division Multiplexing (WDM) sources etc. Comb generation exploiting cascaded four-wave mixing in microresonators have been extensively investigated using materials such as silicon nitride etc. While such nonlinear platforms generate large number of comb lines, they result in combs with fixed centre frequency that is tuneable only in integer multiples of the FSR and fixed repetition rate that is constrained by microresonator dimensions.

We experimentally demonstrate a broadband, fabrication tolerant, CMOS compatible compact silicon waveguide taper (34.2 um) in silicon-on-insulator wire waveguides. The taper works on multi-mode interference along the length of the taper. A single taper design has a broadband operation with coupling efficiency >70% over 700 nm that can be used in O, C and L-band. The compact taper is highly tolerant to fabrication variations; >100 nm change in the taper and end waveguide width varies the taper transmission by, arXiv admin note: substantial text overlap with arXiv:1705.01698

We show modulation in the resonant wavelength of Si micro-ring resonator with mechanically exfoliated graphene using two techniques. Using electrostatic gating, we obtain ~80 pm change in the wavelength. Upon reduction in the gap between graphene and the ring, we obtain ~400 pm change due to graphene.

For quantification of curcumin content in turmeric, a low-cost multivariate-analysis-based sensing system is desired. It can be realized by exploiting the spectra in the visible region, which enables the use of off-the-shelf, relatively inexpensive light sources and detectors. To address this, we propose a novel decision-tree method for improved prediction accuracy. Two sets of models with PLSR algorithm are developed with the measured reflectance spectra from 66 turmeric samples in the range of 360–750 nm, and their respective curcuminoids content are quantified by HPLC. A suite of a coarse-model for initial prediction of turmeric samples in the broad range of 1%–4%, and five finer-models for subsequent prediction (in the ranges 1%–2%, 2%–3%, 3%–4%, 1.5%–2.5%, and 2.5%–3.5%) constitute the proposed decision-tree approach. The method’s efficacy is substantiated from an improved coefficient of determination (R 2) for the finer models (0.90–0.96) as compared to the coarse-model’s 0.92. This is further corroborated with lower RMSECV of 0.06–0.13 and an RMSEP of 0.15–0.25 for finer models, as compared to 0.219 and 0.45 for the coarse model, respectively. Testing reveals that the method results in 46% reduction in prediction error. Realization of a robust prediction approach in the visible range sets the stage for the development of cost-effective field-deployable devices for on-site measurement of curcumin.

We demonstrate a multi-wavelength source with a high repetition rate of 25 GHz, spanning the entire C-band, of which 124 lines lie within 10 dB bandwidth. We exploit the spectral and temporal properties of dual carrier electro-optic combs to simultaneously enhance self-phase modulation (SPM) based broadening and increase the stimulated Brillouin scattering (SBS) threshold. Dual carrier combs are generated through electro-optic modulation of spectrally separated narrow linewidth carriers. They are spectrally broadened in a highly nonlinear fiber after amplification with an in-house built erbium ytterbium co-doped fiber amplifier. The temporal profile of the dual carrier combs consists of significantly narrow pulses (1.4-1.9 ps FWHM) in comparison to the single laser comb (16.5 ps FWHM), increasing the peak power and enhancing the SPM effects. Further, the spectral power is distributed across the comb lines, increasing the SBS threshold and thus the power scalability of the system. These two factors together boost the bandwidth of the spectrally broadened multi-wavelength source.

We demonstrate a technique to continuously tune center frequency and repetition rate of optical frequency combs generated in silicon microring modulators and bandwidth scale them. We utilize a drive frequency dependent, microwave power induced shifting of the microring modulator resonance. In this work, we demonstrate center frequency tunability of frequency combs generated in silicon microring modulators over a wide range (∼8nm) with fixed number of lines. We also demonstrate continuously tunable repetition rates from 7.5GHz to 15GHz. Further, we use this effect to demonstrate a proof-of-principle experiment to bandwidth scale an 8-line (20dB band) comb generated from a single ring modulator driven at 10GHz to a comb with 12 and 15 lines by cascading two and three ring modulators, respectively. This is accomplished by merging widely spaced ring modulator resonances to a common location, thus coupling light simultaneously into multiple cascaded ring modulators.

In this paper, we report phase-pure vanadium dioxide (VO2) deposition on silicon-on-insulator and demonstrate switching/modulation exploiting the phase-change property. We present electrical and optical properties of VO2 during phase transition. Exploiting the phase change property, optical modulation is achieved by thermally tuning the VO2 phase using a lateral micro-heater beside the waveguide. We achieve an optical modulation extinction of 25 dB and a low insertion loss of 1.4 dB using a ring resonator with a VO2 patch. We also demonstrate the switching performance of a symmetric Mach-Zehnder interferometer and present a detailed discussion on the optimal operating point to achieve maximum modulation, higher speed, and lower insertion loss.

A Silicon Nitride assisted SU8 hybrid grating coupler is proposed as a means for coupling to single mode polymer waveguides. Using direct writing approach a patch grating coupler efficiency of -3.9 dB is experimentally demonstrated.

In this work a heterogeneously integrated germanium (Ge) NIR photo-resistor fabricated on CMOS-compatible silicon substrates is presented. The resistor is fabricated on an epitaxial germanium films grown on silicon using a novel liquid phase crystallization (LPC) process. First, silicon wafers were coated with amorphous germanium deposited using PECVD. Next, Ge film is crystallized into epitaxial germanium using a thermal anneal cycle during which Ge undergoes melting and controlled cooling. The LPE Ge films is polycrystalline but epitaxial with threading dislocation density of similar to 10(9) cm(-2). On the LPE germanium, NIR photo-resistors were fabricated with metal-semiconductor-metal (MSM) inter-digitated structure with an active area of 150 mu m x 300 mu m. Responsivity of the devices was characterized using a fiber laser, tunable from 1500 to 1600 nm. With 1550 nm excitation, a photocurrent of 100 mu m was measured at a bias of 4V with laser power of 25 mW, corresponding to a responsivity of 4 mA/W.

We experimentally demonstrate tunable, highly-stable frequency combs with high repetition-rates using a single, charge injection based silicon PN modulator. In this work, we demonstrate combs in the C-band with over 8 lines in a 20-dB bandwidth. We demonstrate continuous tuning of the center frequency in the C-band and tuning of the repetition-rate from 7.5GHz to 12.5GHz. We also demonstrate through simulations the potential for bandwidth scaling using an optimized silicon PIN modulator. We find that, the time varying free carrier absorption due to carrier injection, an undesirable effect in data modulators, assists here in enhancing flatness in the generated combs., Comment: 10 pages, 7 figures

We demonstrate a compact efficient waveguide taper in Silicon Nitride platform. The proposed taper provides a coupling-efficiency of 95p at a length of 19.5 μm in comparison to the standard linear taper of length 50 μm that connects a 10 μm wide waveguide to a 1 μm wide photonic wire. The taper has a spectral response > 75p spanning over 800 nm (spanning O, C & L band) and robustness to fabrication variations; ±200 nm change in taper and end waveguide width varies transmission by

We propose and demonstrate a Silicon MSM photodetector integrated on Silicon Nitride-on-SOI platform. The demonstration shows the feasibility of an integrated photonic circuit platform in the visible to NIR wavelength with an integrated Silicon photodetector. We present a planarization free oxidation based Silicon Nitride waveguide fabrication on SOI. DC measurements on photo-detectors with the top illumination of 850 nm light observe the best responsivity of 0.1 A/W at 20 V with a dark current of 570 nA.

Optical-Printed Circuit Board (PCB) is an emerging optical interconnect technology to bridge the gap between the board edge and the processing module. The technology so far has been used as a broadband transmitter using polymer waveguides in the PCB. In this paper, we report a Silicon Nitride based photonic IC embedded in the PCB along with the polymers as waveguides in the PCB. The motivation for such integration is to bring routing capability and to reduce the power loss due to broadcasting mode.

We demonstrate an all optical four channel multicasting using Silicon photonic coupled cavity. An aggregate data rate of 7.2Gbps is transmitted. The proposed cavity system breaks the inherent free spectral range and cavity length product relationship. Multicasting is achieved using free carrier dispersion in Silicon induced by a modulated pump which is mapped to four optical channels.

We present a Silicon photonics assisted RF signal processing, in particular, frequency doubling and RF pulse generation. We demonstrate frequency doubling till 10 GHz using silicon PN ring resonator and we present a detailed study on the effect of carrier offset on the power and linewidth of the up-converted RF signal by increasing the Local Oscillator(LO) frequency. We also demonstrate a photonics approach of pulse generation using an on-chip Silicon PN Mach-Zehnder modulator, where RF-signal frequency between 1–12 GHz could be fed and pulsed at various rates from 100–0.1 millisecond.

We demonstrate high-speed Silicon pin photodetector integrated with SiN waveguide. Optimized waveguide-photodetector coupling yields maximum responsivity of 0.44A/W and highest ever bandwidth of 15.5GHz for waveguide integrated Silicon photodetector.

We demonstrate an all-optical four-channel wavelength multicasting in a coupled silicon microring resonator system. The scheme is based on two-photon-absorption-induced free carrier dispersion in silicon. The coupled cavity facilitates resonance splitting that is utilized as individual channels for multicasting. Using the split resonances, we achieve an aggregate multicasted data rate of 48 Gbps (4 × 12 Gbps). Moreover, we also present a detailed analysis and performance of the multicasting architecture using bit error rate and eye diagram measurements.

This paper presents a novel robust method to excite a slot waveguide mode. We experimentally demonstrate the fundamental slot-mode excitation in a Si slot-waveguide ring resonator. Furthermore, we also demonstrate nearly athermal (12 pm/°C) behaviour of PMMA filled slotted ring resonator.

We propose and demonstrate a self-coupled micro-ring resonator for resonance splitting by mutual mode coupling of a cavity mode and a counter-propagating mode in a silicon-on-insulator platform. The resonator is constructed with a self-coupling region that can excite a counter-propagating mode. We experimentally study the effect of self-coupling on the resonance splitting, resonance extinction, and quality-factor evolution and stability. Based on the coupling, we achieve 72% of the free spectral range (FSR) splitting for a cavity with an FSR of 2.1 nm with5% variation in the cavity quality factor. The self-coupled resonance splitting shows a highly robust spectral characteristic that can be exploited for sensing and optical signal processing.

We present a diffusion doping based plasma dispersion optical modulator in Silicon-On-Insulator platform. To the best of our knowledge this is the first demonstration of a diffusion-doped (Boron and Phosphorus) modulator in a compact Silicon waveguide. However, it results in a graded, isotropic doping profile where lateral diffusion length of the dopants is a critical parameter. We use a micro-ring resonator and proximity doping with varying offset besides the waveguide to experimentally measure the lateral diffusion length. The lateral diffusion is characterized from the change in the extinction of the ring resonator. Experimental measurement shows a lateral diffusion length of 1600 nm in a 220 nm thick Si device layer, which agrees well with the theoretical calculation. With the lateral dopant diffusion length, we have designed and fabricated a 1 mm long pn MZI modulator. Fabrication was done using a combination of optical and e-beam lithography. The MZI waveguides were defined with 160 nm etch in a 220 nm device layer with a waveguide width of 450 nm. As an initial demonstration, we show plasma dispersion based spectral blue shift of 1.5 nm with a reverse-bias voltage of 5 V.

Low-loss deposited amorphous silicon ( α -Si:H) layers for nano-photonic integrated circuit have been prepared using complementary-metal-oxide-semiconductor (CMOS) compatible technology. Waveguide loss as low as 3.45 dB/cm is reported for films deposited at a low temperature (300 °C) using plasma enhanced chemical vapour deposition process. The influence of the deposition parameters such as gas dilution, plasma power and pressure on the quality of the deposited material is thoroughly characterized using Fourier transform infrared spectroscopy (FTIR), spectroscopic ellipsometry, X-ray diffraction and atomic force microscopy. We show that the optical quality of the deposited film can be directly assessed from distinct frequency bands (2090, 2000 and 840 cm −1 ) using FTIR, without the need for further waveguide loss measurements.

High repetition-rate frequency combs with tunable repetition rate and carrier frequency are extensively used in areas like Optical communications, Microwave Photonics and Metrology. A common technique for their generation is strong phase modulation of a CW-laser. This is commonly implemented using Lithium-Niobate based modulators. With phase modulation alone, the combs have poor spectral flatness and significant number of missing lines. To overcome this, a complex cascade of multiple intensity and phase modulators are used. A comb generator on Silicon based on these principles is desirable to enable on-chip integration with other functionalities while reducing power consumption and footprint. In this work, we analyse frequency comb generation in carrier injection based Silicon modulators. We observe an interesting effect in these comb generators. Enhanced absorption accompanying carrier injection, an undesirable effect in data modulators, shapes the amplitude here to enable high quality combs from a single modulator. Thus, along with reduced power consumption to generate a specific number of lines, the complexity has also been significantly reduced. We use a drift-diffusion solver and mode solver (Silvaco TCAD) along with Soref-Bennett relations to calculate the variations in refractive indices and absorption of an optimized Silicon PIN - waveguide modulator driven by an unbiased high frequency (10 Ghz) voltage signal. Our simulations demonstrate that with a device length of 1 cm, a driving voltage of 2V and minor shaping with a passive ring-resonator filter, we obtain 37 lines with a flatness better than 5-dB across the band and power consumption an order of magnitude smaller than Lithium-Niobate modulators.

Various configurations of ring resonator based delay lines have been studied analytically. A ring inside ring configuration is proposed to achieve a delay of ~300 ps (ER ~ 90%) with a device footprint ~0.03 mm2.

In this paper, we present Silicon micro-ring resonator based technique to measure lateral diffusion length of dopants in Silicon. We experimentally demonstrate a lateral diffusion length of 1400 nm that agrees well with the simulation.

Silicon nitride is a promising high-index material for dense photonic circuits and applications in the visible-midinfrared wavelength regime. Design, fabrication, and optical characterization of silicon nitride waveguides at visible-near-infrared wavelength are presented. Finally, design and experimental results are presented for the first time for linear and focused grating couplers (GCs) at near-infrared wavelength (900 nm) for plasma-enhanced chemical vapor deposition silicon nitride wires (220 x 500 nm) and compared with theoretical simulations. An experimental efficiency of 5.7 and 6.5 dB and 1-dB bandwidth of 26 and 40 nm are reported for the linear and focused GCs, respectively.

Single mode silicon photonic wire waveguides allow low-loss sharp micro-bends, which enables compact photonic devices and circuits. The circuit compactness is achieved at the cost of loss induced by micro-bends, which can seriously affect the device performance. The bend loss strongly depends on the bend radius, polarization, waveguide dimension and profile. In this paper, we present the effect of waveguide profile on the bend loss. We present waveguide profile improvement with optimized etch chemistry and the role of etch chemistry in adapting the etch profile of silicon is investigated. We experimentally demonstrate that by making the waveguide sidewalls vertical, the bend loss can be reduced up to 25% without affecting the propagation loss of the photonic wires. The bend loss of a 2 μm bend has been reduced from 0.039dB/90° bend to 0.028dB/90° bend by changing the sidewall angle from 81° to 90°, respectively. The propagation loss of 2.7 ± 0.1dB/cm and 3 ± 0.09dB/cm was observed for sloped and vertical photonic wires respectively was obtained.