Sanja Radosavljevic | Ghent University (original) (raw)
Papers by Sanja Radosavljevic
Optics Express, Jul 28, 2017
We present the design, fabrication and characterization of efficient fiber-to-chip grating couple... more We present the design, fabrication and characterization of efficient fiber-to-chip grating couplers on a Germanium-on-Silicon (Ge-on-Si) and Germanium-on-silicon-on-insulator (Ge-on-SOI) platform in the 5 µm wavelength range. The best grating couplers on Ge-on-Si and Ge-on-SOI have simulated coupling efficiencies of-4 dB (40%) with a 3 dB bandwidth of 180 nm and-1.5 dB (70%) with a 3 dB bandwidth of 200 nm, respectively. Experimentally, we show a maximum efficiency of-5 dB (32%) and a 3 dB bandwidth of 100 nm for Ge-on-Si grating couplers, and a-4 dB (40%) efficiency with a 3 dB bandwidth of 180 nm for Ge-on-SOI couplers.
We review our work on SOI and Ge-on-SOI PICs for the mid-infrared. We demonstrate the integration... more We review our work on SOI and Ge-on-SOI PICs for the mid-infrared. We demonstrate the integration of III-V semiconductors on the SOI platform for 2-4 µm wavelength range integrated lasers and spectrometers, as well as tunable filters implemented on the Ge-on-SOI platform beyond 4µm.
IEEE Journal of Selected Topics in Quantum Electronics, Nov 1, 2019
Quantum cascade lasers (QCLs) are essential components for mid-infrared optical spectroscopy. Cur... more Quantum cascade lasers (QCLs) are essential components for mid-infrared optical spectroscopy. Currently, widely tunable QCLs are using an external diffraction grating to tune the laser wavelength. In this paper we present a compact tunable QCL that is thermally tuned by a distributed Bragg reflector (DBR) implemented on a Germanium-on-SOI (Ge-on-SOI) waveguide circuit. The 5.1x µm wavelength laser, operating in pulsed mode at room temperature, is continuously tuned over 50 nm.
We present efficient TM fiber-to-chip grating couplers that couple light between a single mode In... more We present efficient TM fiber-to-chip grating couplers that couple light between a single mode InF fiber and Germanium-on-Silicon (Ge-on-Si) waveguides in the 5 μm wavelength range. In recent years, Ge-on-Si has emerged as a platform of interest for sensing applications beyond 4 μm [1, 2]. Ge has low losses for light in the 4-12 μm range, which makes it suitable for the realization of mid-infrared (midIR) photonic integrated circuit gas and liquid sensors.
Conference on Lasers and Electro-Optics, 2018
We present a Vernier tunable racetrack resonator filter on Ge-on-SOI, with 110 nm FSR at 5 μm. Th... more We present a Vernier tunable racetrack resonator filter on Ge-on-SOI, with 110 nm FSR at 5 μm. The racetrack has a Q-factor of 20000 and side-peak suppression >20 dB, sufficient for wavelength selection in an external cavity laser.
Universiteit Gent. Faculteit Ingenieurswetenschappen en Architectuur, 2020
Optical Sensors and Sensing Congress, 2020
An in-line sensing platform for detecting contaminants in aqueous solution is presented, comprisi... more An in-line sensing platform for detecting contaminants in aqueous solution is presented, comprising Ge waveguides, microlenses and grating couplers for rapid interfacing with mid-IR spectrometers, and a hydrophobic mesoporous layer for selectivity toward apolar contaminants.
2018 IEEE 15th International Conference on Group IV Photonics (GFP), 2018
We review our work on SOI and Ge-on-SOI PICs for the mid-infrared. We demonstrate the integration... more We review our work on SOI and Ge-on-SOI PICs for the mid-infrared. We demonstrate the integration of III-V semiconductors on the SOI platform for 2-4 µm wavelength range integrated lasers and spectrometers, as well as tunable filters implemented on the Ge-on-SOI platform beyond 4µm.
We present efficient TM fiber-to-chip grating couplers that couple light between a single mode In... more We present efficient TM fiber-to-chip grating couplers that couple light between a single mode InF fiber and Germanium-on-Silicon (Ge-on-Si) waveguides in the 5 μm wavelength range. In recent years, Ge-on-Si has emerged as a platform of interest for sensing applications beyond 4 μm [1, 2]. Ge has low losses for light in the 412 μm range, which makes it suitable for the realization of mid-infrared (midIR) photonic integrated circuit gas and liquid sensors. Fig 1. Simulated fiber-to-chip coupling efficiency as a function of wavelength (a) and the measured couping efficiency of the grating (b) Grating coupler design: Since for a number of midIR applications QCL sources are used, emitting TM polarized light, we have opted to design fiber-chip interfaces for TM polarization. The couplers are designed in a 2 μm thick Ge waveguide layer on a silicon substrate. The TM grating coupler for the Ge-on-Si platform has a period of 1.42 μm, a 80% duty cycle (defined as the ratio of the width of th...
Slot waveguides can improve the sensitivity of biosensors by enhancing the interaction between th... more Slot waveguides can improve the sensitivity of biosensors by enhancing the interaction between the optical field and the biomolecules. Slot microrings have been demonstrated on high refractive index (RI) materials such as silicon and silicon nitride. In this paper, polymeric slot microrings are studied for applications in biosensors. Slot width and waveguide width have been optimized to get a high sensitivity and low bend loss. Compared with common polymeric microring biosensosr, slot waveguide microrings can achieve 110 nm/RIU which is more than double the sensitivity of normal polymeric microring biosensors.
We present the design of fiber-to-chip grating couplers on Germanium-on-Silicon (Ge-onSi) and Ger... more We present the design of fiber-to-chip grating couplers on Germanium-on-Silicon (Ge-onSi) and Germanium on silicon-on-insulator (Ge-on-SOI) waveguides in the 5μm wavelength range. The best TM and TE grating couplers for Ge-on-Si have a coupling efficiency of 40% and 16% respectively with 3dB bandwidths of 180nm and 220nm at a central wavelength around 5.3μm. The best grating couplers for Ge-on-SOI have a coupling efficiency of 70% for the TM mode and 60% for the TE mode. The higher coupling efficiency to Ge-on-SOI waveguides is attributed to the strong reflection at the Si/air interface of the free-standing grating, which can be optimized for maximum coupling efficiency.
Optics Express, 2020
A novel platform based on evanescent wave sensing in the 6.5 to 7.5 µm wavelength range is presen... more A novel platform based on evanescent wave sensing in the 6.5 to 7.5 µm wavelength range is presented with the example of toluene detection in an aqueous solution. The overall sensing platform consists of a germanium-on-silicon waveguide with a functionalized mesoporous silica cladding and integrated microlenses for alignment-tolerant back-side optical interfacing with a tunable laser spectrometer. Hydrophobic functionalization of the mesoporous cladding allows enrichment of apolar analyte molecules and prevents strong interaction of water with the evanescent wave. The sensing performance was evaluated for aqueous toluene standards resulting in a limit of detection of 7 ppm. Recorded adsorption/desorption profiles followed Freundlich adsorption isotherms with rapid equilibration and resulting sensor response times of a few seconds. This indicates that continuous monitoring of contaminants in water is possible. A significant increase in LOD can be expected by likely improvements to th...
OSA Optical Sensors and Sensing Congress 2021 (AIS, FTS, HISE, SENSORS, ES), 2021
Germanium-on-Silicon waveguide chips coated with functionalized mesoporous silica were used for e... more Germanium-on-Silicon waveguide chips coated with functionalized mesoporous silica were used for evanescent wave sensing of organic contaminants in gas and aqueous phase. Low ppm level LODs and fast response times pave the way for in-line monitoring.
IEEE Journal of Selected Topics in Quantum Electronics, 2019
Quantum cascade lasers (QCLs) are essential components for mid-infrared optical spectroscopy. Cur... more Quantum cascade lasers (QCLs) are essential components for mid-infrared optical spectroscopy. Currently, widely tunable QCLs are using an external diffraction grating to tune the laser wavelength. In this paper we present a compact tunable QCL that is thermally tuned by a distributed Bragg reflector (DBR) implemented on a Germanium-on-SOI (Ge-on-SOI) waveguide circuit. The 5.1x µm wavelength laser, operating in pulsed mode at room temperature, is continuously tuned over 50 nm.
![Research paper thumbnail of Mid-infrared Vernier racetrack resonator tunable filter implemented on a germanium on SOI waveguide platform [Invited]](https://attachments.academia-assets.com/120087862/thumbnails/1.jpg)
](Optical Materials Express, 2018
Currently, most widely tunable lasers rely on an external diffraction grating to tune the laser w... more Currently, most widely tunable lasers rely on an external diffraction grating to tune the laser wavelength. In this paper we present the realization of a chip-scale Vernier tunable racetrack resonator filter on the Ge-on-SOI waveguide platform that allows for wide tuning (108 nm free spectral range) in the 5 µm wavelength range without any moving parts. The fabricated racetrack resonators have a loaded Q-factor of 20000, resulting in a side-peak suppression of more than 20 dB, which is more than sufficient for wavelength selection in an external cavity laser.
Optics Express, 2017
We present the design, fabrication and characterization of efficient fiber-to-chip grating couple... more We present the design, fabrication and characterization of efficient fiber-to-chip grating couplers on a Germanium-on-Silicon (Ge-on-Si) and Germanium-on-silicon-on-insulator (Ge-on-SOI) platform in the 5 µm wavelength range. The best grating couplers on Ge-on-Si and Ge-on-SOI have simulated coupling efficiencies of-4 dB (40%) with a 3 dB bandwidth of 180 nm and-1.5 dB (70%) with a 3 dB bandwidth of 200 nm, respectively. Experimentally, we show a maximum efficiency of-5 dB (32%) and a 3 dB bandwidth of 100 nm for Ge-on-Si grating couplers, and a-4 dB (40%) efficiency with a 3 dB bandwidth of 180 nm for Ge-on-SOI couplers.
Physics Letters A, 2016
Tunneling times in complex bianisotropic materials have been examined in detail, with absorption ... more Tunneling times in complex bianisotropic materials have been examined in detail, with absorption and dispersion taken into account. Tunneling is characterized by the dwell and the phase tunneling time. In this paper, we have developed a theoretical model and derived the appropriate expressions for each of these quantities, as well as a relationship between them and the corresponding expression for the energy density. The model has been verified through numerical calculations based on experimental data. We have distinguished cases in which the phases of transmitted and incident wave match each other, and showed that for small angles of incidence, the time that the wave spends inside the barrier can be approximated as a linear function of the barrier width. The Hartman effect has been detected, although for very thick layers of metamaterial.
Procedia Engineering, 2016
Silicon-based photonic integrated circuits (PICs) operating in the mid-infrared wavelength range ... more Silicon-based photonic integrated circuits (PICs) operating in the mid-infrared wavelength range are presented. Firstly, it is shown that the operation of the SOI-based waveguide circuits can be pushed beyond the telecom window till a wavelength of 4 µm. Ge-on-Si based PICs are demonstrated for operation beyond 4 µm wavelength. Low-loss waveguides and integrated spectrometers are reported for both the waveguide platforms. We also present our results on efficient thermo-optic phase shifters for germanium waveguide circuits.
Optics Express, Jul 28, 2017
We present the design, fabrication and characterization of efficient fiber-to-chip grating couple... more We present the design, fabrication and characterization of efficient fiber-to-chip grating couplers on a Germanium-on-Silicon (Ge-on-Si) and Germanium-on-silicon-on-insulator (Ge-on-SOI) platform in the 5 µm wavelength range. The best grating couplers on Ge-on-Si and Ge-on-SOI have simulated coupling efficiencies of-4 dB (40%) with a 3 dB bandwidth of 180 nm and-1.5 dB (70%) with a 3 dB bandwidth of 200 nm, respectively. Experimentally, we show a maximum efficiency of-5 dB (32%) and a 3 dB bandwidth of 100 nm for Ge-on-Si grating couplers, and a-4 dB (40%) efficiency with a 3 dB bandwidth of 180 nm for Ge-on-SOI couplers.
We review our work on SOI and Ge-on-SOI PICs for the mid-infrared. We demonstrate the integration... more We review our work on SOI and Ge-on-SOI PICs for the mid-infrared. We demonstrate the integration of III-V semiconductors on the SOI platform for 2-4 µm wavelength range integrated lasers and spectrometers, as well as tunable filters implemented on the Ge-on-SOI platform beyond 4µm.
IEEE Journal of Selected Topics in Quantum Electronics, Nov 1, 2019
Quantum cascade lasers (QCLs) are essential components for mid-infrared optical spectroscopy. Cur... more Quantum cascade lasers (QCLs) are essential components for mid-infrared optical spectroscopy. Currently, widely tunable QCLs are using an external diffraction grating to tune the laser wavelength. In this paper we present a compact tunable QCL that is thermally tuned by a distributed Bragg reflector (DBR) implemented on a Germanium-on-SOI (Ge-on-SOI) waveguide circuit. The 5.1x µm wavelength laser, operating in pulsed mode at room temperature, is continuously tuned over 50 nm.
We present efficient TM fiber-to-chip grating couplers that couple light between a single mode In... more We present efficient TM fiber-to-chip grating couplers that couple light between a single mode InF fiber and Germanium-on-Silicon (Ge-on-Si) waveguides in the 5 μm wavelength range. In recent years, Ge-on-Si has emerged as a platform of interest for sensing applications beyond 4 μm [1, 2]. Ge has low losses for light in the 4-12 μm range, which makes it suitable for the realization of mid-infrared (midIR) photonic integrated circuit gas and liquid sensors.
Conference on Lasers and Electro-Optics, 2018
We present a Vernier tunable racetrack resonator filter on Ge-on-SOI, with 110 nm FSR at 5 μm. Th... more We present a Vernier tunable racetrack resonator filter on Ge-on-SOI, with 110 nm FSR at 5 μm. The racetrack has a Q-factor of 20000 and side-peak suppression >20 dB, sufficient for wavelength selection in an external cavity laser.
Universiteit Gent. Faculteit Ingenieurswetenschappen en Architectuur, 2020
Optical Sensors and Sensing Congress, 2020
An in-line sensing platform for detecting contaminants in aqueous solution is presented, comprisi... more An in-line sensing platform for detecting contaminants in aqueous solution is presented, comprising Ge waveguides, microlenses and grating couplers for rapid interfacing with mid-IR spectrometers, and a hydrophobic mesoporous layer for selectivity toward apolar contaminants.
2018 IEEE 15th International Conference on Group IV Photonics (GFP), 2018
We review our work on SOI and Ge-on-SOI PICs for the mid-infrared. We demonstrate the integration... more We review our work on SOI and Ge-on-SOI PICs for the mid-infrared. We demonstrate the integration of III-V semiconductors on the SOI platform for 2-4 µm wavelength range integrated lasers and spectrometers, as well as tunable filters implemented on the Ge-on-SOI platform beyond 4µm.
We present efficient TM fiber-to-chip grating couplers that couple light between a single mode In... more We present efficient TM fiber-to-chip grating couplers that couple light between a single mode InF fiber and Germanium-on-Silicon (Ge-on-Si) waveguides in the 5 μm wavelength range. In recent years, Ge-on-Si has emerged as a platform of interest for sensing applications beyond 4 μm [1, 2]. Ge has low losses for light in the 412 μm range, which makes it suitable for the realization of mid-infrared (midIR) photonic integrated circuit gas and liquid sensors. Fig 1. Simulated fiber-to-chip coupling efficiency as a function of wavelength (a) and the measured couping efficiency of the grating (b) Grating coupler design: Since for a number of midIR applications QCL sources are used, emitting TM polarized light, we have opted to design fiber-chip interfaces for TM polarization. The couplers are designed in a 2 μm thick Ge waveguide layer on a silicon substrate. The TM grating coupler for the Ge-on-Si platform has a period of 1.42 μm, a 80% duty cycle (defined as the ratio of the width of th...
Slot waveguides can improve the sensitivity of biosensors by enhancing the interaction between th... more Slot waveguides can improve the sensitivity of biosensors by enhancing the interaction between the optical field and the biomolecules. Slot microrings have been demonstrated on high refractive index (RI) materials such as silicon and silicon nitride. In this paper, polymeric slot microrings are studied for applications in biosensors. Slot width and waveguide width have been optimized to get a high sensitivity and low bend loss. Compared with common polymeric microring biosensosr, slot waveguide microrings can achieve 110 nm/RIU which is more than double the sensitivity of normal polymeric microring biosensors.
We present the design of fiber-to-chip grating couplers on Germanium-on-Silicon (Ge-onSi) and Ger... more We present the design of fiber-to-chip grating couplers on Germanium-on-Silicon (Ge-onSi) and Germanium on silicon-on-insulator (Ge-on-SOI) waveguides in the 5μm wavelength range. The best TM and TE grating couplers for Ge-on-Si have a coupling efficiency of 40% and 16% respectively with 3dB bandwidths of 180nm and 220nm at a central wavelength around 5.3μm. The best grating couplers for Ge-on-SOI have a coupling efficiency of 70% for the TM mode and 60% for the TE mode. The higher coupling efficiency to Ge-on-SOI waveguides is attributed to the strong reflection at the Si/air interface of the free-standing grating, which can be optimized for maximum coupling efficiency.
Optics Express, 2020
A novel platform based on evanescent wave sensing in the 6.5 to 7.5 µm wavelength range is presen... more A novel platform based on evanescent wave sensing in the 6.5 to 7.5 µm wavelength range is presented with the example of toluene detection in an aqueous solution. The overall sensing platform consists of a germanium-on-silicon waveguide with a functionalized mesoporous silica cladding and integrated microlenses for alignment-tolerant back-side optical interfacing with a tunable laser spectrometer. Hydrophobic functionalization of the mesoporous cladding allows enrichment of apolar analyte molecules and prevents strong interaction of water with the evanescent wave. The sensing performance was evaluated for aqueous toluene standards resulting in a limit of detection of 7 ppm. Recorded adsorption/desorption profiles followed Freundlich adsorption isotherms with rapid equilibration and resulting sensor response times of a few seconds. This indicates that continuous monitoring of contaminants in water is possible. A significant increase in LOD can be expected by likely improvements to th...
OSA Optical Sensors and Sensing Congress 2021 (AIS, FTS, HISE, SENSORS, ES), 2021
Germanium-on-Silicon waveguide chips coated with functionalized mesoporous silica were used for e... more Germanium-on-Silicon waveguide chips coated with functionalized mesoporous silica were used for evanescent wave sensing of organic contaminants in gas and aqueous phase. Low ppm level LODs and fast response times pave the way for in-line monitoring.
IEEE Journal of Selected Topics in Quantum Electronics, 2019
Quantum cascade lasers (QCLs) are essential components for mid-infrared optical spectroscopy. Cur... more Quantum cascade lasers (QCLs) are essential components for mid-infrared optical spectroscopy. Currently, widely tunable QCLs are using an external diffraction grating to tune the laser wavelength. In this paper we present a compact tunable QCL that is thermally tuned by a distributed Bragg reflector (DBR) implemented on a Germanium-on-SOI (Ge-on-SOI) waveguide circuit. The 5.1x µm wavelength laser, operating in pulsed mode at room temperature, is continuously tuned over 50 nm.
Optical Materials Express, 2018
Currently, most widely tunable lasers rely on an external diffraction grating to tune the laser w... more Currently, most widely tunable lasers rely on an external diffraction grating to tune the laser wavelength. In this paper we present the realization of a chip-scale Vernier tunable racetrack resonator filter on the Ge-on-SOI waveguide platform that allows for wide tuning (108 nm free spectral range) in the 5 µm wavelength range without any moving parts. The fabricated racetrack resonators have a loaded Q-factor of 20000, resulting in a side-peak suppression of more than 20 dB, which is more than sufficient for wavelength selection in an external cavity laser.
Optics Express, 2017
We present the design, fabrication and characterization of efficient fiber-to-chip grating couple... more We present the design, fabrication and characterization of efficient fiber-to-chip grating couplers on a Germanium-on-Silicon (Ge-on-Si) and Germanium-on-silicon-on-insulator (Ge-on-SOI) platform in the 5 µm wavelength range. The best grating couplers on Ge-on-Si and Ge-on-SOI have simulated coupling efficiencies of-4 dB (40%) with a 3 dB bandwidth of 180 nm and-1.5 dB (70%) with a 3 dB bandwidth of 200 nm, respectively. Experimentally, we show a maximum efficiency of-5 dB (32%) and a 3 dB bandwidth of 100 nm for Ge-on-Si grating couplers, and a-4 dB (40%) efficiency with a 3 dB bandwidth of 180 nm for Ge-on-SOI couplers.
Physics Letters A, 2016
Tunneling times in complex bianisotropic materials have been examined in detail, with absorption ... more Tunneling times in complex bianisotropic materials have been examined in detail, with absorption and dispersion taken into account. Tunneling is characterized by the dwell and the phase tunneling time. In this paper, we have developed a theoretical model and derived the appropriate expressions for each of these quantities, as well as a relationship between them and the corresponding expression for the energy density. The model has been verified through numerical calculations based on experimental data. We have distinguished cases in which the phases of transmitted and incident wave match each other, and showed that for small angles of incidence, the time that the wave spends inside the barrier can be approximated as a linear function of the barrier width. The Hartman effect has been detected, although for very thick layers of metamaterial.
Procedia Engineering, 2016
Silicon-based photonic integrated circuits (PICs) operating in the mid-infrared wavelength range ... more Silicon-based photonic integrated circuits (PICs) operating in the mid-infrared wavelength range are presented. Firstly, it is shown that the operation of the SOI-based waveguide circuits can be pushed beyond the telecom window till a wavelength of 4 µm. Ge-on-Si based PICs are demonstrated for operation beyond 4 µm wavelength. Low-loss waveguides and integrated spectrometers are reported for both the waveguide platforms. We also present our results on efficient thermo-optic phase shifters for germanium waveguide circuits.