Nonlinear photonics in silicon germanium waveguides for mid-infrared supercontinuum generation

Mid-infrared light (2.5 - 15 um) can be advantageously used for high-sensitivity molecular detection in environment, healthcare, industry and security applications. Various molecules can be detected at trace levels by measuring their strong absorption that is several orders of magnitude stronger in the mid-infrared than in the near-infrared. In recent years, there has been a high demand for compact mid-infrared sensors that can be equipped within cars, drones or even smartphones. These sensors could be realized by relying on a technology that is used in a cost-effective micro-electronics industry. The field of photonics utilizing the complementary metal-oxide-semiconductor technology is referred to as silicon photonics. The envisioned compact (on-chip) mid-infrared sensor consists of a light source, sensing area, and photo-detector. The scope of this thesis has been to develop the first building block of this sensor, which is the mid-infrared supercontinuum light source on a silicon-based chip. Supercontinuum (SC) light is particularly interesting for molecular spectroscopy as it allows for accessing multiple absorption wavelengths at once, enabling the reliable and simultaneous detection of many molecules. Mid-infrared supercontinua on a silicon-based chip have been reported in several platforms on insulating substrates, i.e. silica and sapphire. However, the operation wavelength ranges in these platforms are limited to 3.7 and 5.5 um due to the absorption in silica and sapphire, respectively. The main goals of this thesis have been to explore a silicon-based platform with extended wavelength range deeper in the mid-infrared and to demonstrate a spectrally bright supercontinuum beyond 5.5um. Such a supercontinuum would cover the entire mid-infrared atmospheric absorption band from 4 to 8 um. In addition to high brightness, ultra-fast and high-precision molecular spectroscopy requires high coherence of a supercontinuum. In this context, an additional objective has been to achieve a coherent supercontinuum generation. Germanium is a well-known material in the microelectronics industry which has been suggested for silicon photonics in the mid-infrared owing to its wide transparency window. However, the lattice mismatch between germanium and silicon eventually leads to a large density of threading dislocations at the germanium/silicon interface, which limits the performance of nonlinear optical devices. Our solution to this issue has been to use a silicon germanium-on-silicon platform with 40% of germanium in the alloy. Silicon germanium waveguides buried in silicon, which were not dispersion engineered for supercontinuum, were explored in our group. In these waveguides, L. Carletti demonstrated a promising low loss operation and identified an optimal operation wavelength at around 4um. Based on these initial results; I designed air clad waveguides and optimized their dispersion for supercontinuum generation. The waveguides used in this thesis were fabricated using a technological process developed over the last two decades by our collaborators at the micro and nanotechnology research center CEA-Leti in Grenoble, France. The experiments were then performed at the Laser Physics Centre at Australian National University (ANU) in Canberra, Australia. There, we performed linear and nonlinear measurements using a picosecond and sub-picosecond pump at 4um in wavelength. The experimental results were analyzed using an in-house developed software. The measured supercontinuum spectra/transmission fits and coherence properties have been analyzed using a generalized nonlinear Schrodinger equation solver. Dispersion trimming presented in the fourth chapter has been investigated using a custom-built mode solver. The theory of nonlinear optics used in this thesis is introduced in the first chapter. The second chapter reports a spectrally bright supercontinuum spanning to 8.5um from a dispersion-engineered silicon germanium-on-silicon waveguide. This is a milestone in the mid-infrared silicon photonics since the supercontinuum reached the onset of silicon absorption at 8.5um. In this waveguide, we measured a propagation loss as low as 0.2 dB/cm and more than 10mW on chip supercontinuum power. This is the lowest measured loss and the largest supercontinuum power reported in any silicon-based waveguide in the mid-infrared. The third chapter discusses the coherence of an octave-spanning supercontinuum. Coherence has been numerically analyzed for an experimentally measured supercontinuum. This chapter shows that a high coherence can be achieved in a long waveguide pumped in the anomalous dispersion regime with 200fs pulses. This is possible thanks to the specific dispersion profile with a relatively narrow anomalous dispersion band. In the last chapter, we demonstrate a simple post-fabrication dispersion trimming technique that can be used to optimize dispersion or to shift dispersion from anomalous to all normal. The mid-infrared possesses the fundamental barrier for standard silicon-based platforms including silicon-on-insulator, silicon nitride-on-insulator, and silicon-on-sapphire. The results reported in this thesis clearly establish silicon germanium-on-silicon as a relevant platform for nonlinear silicon photonics in the mid-infrared. The octave-spanning coherent supercontinuum that has been demonstrated paves the way for future mid-infrared molecule sensor on a silicon chip

ages of women at the time of marriage: the example of ancient Salona

U epigrafskome materijalu antičke Salone postoji mala grupa nadgrobnih spomenika koji bilježe starosnu dob žena u vrijeme smrti i trajanje braka. Oni su izvrstan izvor podataka o braku, kvaliteti življenja žena i općenito društvenim prilikama u salonitanskom društvu. Ljudi zabilježeni na ovim epitafima pripadali su uglavnom srednje imućnom društvenom staležu koji se razvio u urbanim središtima Rimskoga Carstva. Među njima se pojavljuju oslobođenici/oslobođenice, slobodni građani/građanke, ali i robovi/ropkinje. Nadgrobni spomenici ovog karaktera nisu bili česta pojava u Rimskome Carstvu. Najvećim dijelom evidentirani su u gradovima antičke Italije, dok ih je jedan manji broj pronađen u provincijskim središtima Afrike, Dalmacije i Panonije.Among the epigraphic records from Roman-era Salona, there is a small group of grave monuments that record the age of women at the time of their death and the duration of their marriage. These are an outstanding source of data on marriage, the quality of life of women, and overall social circumstances in Salona. The people commemorated in these epigraphs generally belonged to the well-to-do middle class that emerged in urban centres of the Roman Empire. Among them there were freedmen/women, free citizens of both sexes, but also slaves. Grave monuments of this character were not common in the Roman Empire. They were mostly documented in the cities of ancient Italy, while only a smaller number has been found in the provincial centres of Africa, Dalmatia and Pannonia

Watt-class CMOS-compatible power amplifier

Power amplifier is becoming a critical component for integrated photonics as the integrated devices try to carve out a niche in the world of real-world applications of photonics. That is because the signal generated from an integrated device severely lacks in power which is due mainly to the small size which, although gives size and weight advantage, limits the energy storage capacity of an integrated device due to the small volume, causing it to rely on its bench-top counterpart for signal amplification downstream. Therefore, an integrated high-power signal booster can play a major role by replacing these large solid-state and fiber-based benchtop systems. For decades, large mode area (LMA) technology has played a disruptive role by increasing the signal power and energy by orders of magnitude in the fiber-based lasers and amplifiers. Thanks to the capability of LMA fiber to support significantly larger optical modes the energy storage and handling capability has significantly increased. Such an LMA device on an integrated platform can play an important role for high power applications. In this work, we demonstrate LMA waveguide based CMOS compatible watt-class power amplifier with an on-chip output power reaching ~ 1W within a footprint of ~4mm2.The power achieved is comparable and even surpasses many fiber-based amplifiers. We believe this work opens up opportunities for integrated photonics to find real world application on-par with its benchtop counterpart

Evaluation of photometric methods in assessment of dimensional stability of elastomeric impression materials

U stomatologiji se otisni materijali upotrebljavaju za reprodukciju oblika i odnosa zuba i okolnih oralnih tkiva, a dobijeni otisci se koriste za izradu dijagnostičkih i master modela. Dimenzionalna stabilnost elastomernih otisnih materijala u različitim uslovima, važan je faktor koji direktno utiče na preciznost i trajnost indirektno izrađenih definitivnih zubnih nadoknada. Definiše se kao sposobnost materijala da zadrži svoju veličinu i oblik tokom vremena. Cilj ovog istraživanja je ispitivanje različitih mogućnosti originalnih fotometrijskih metoda u proceni dimenzionalne stabilnosti elastomernih otisnih materijala i utvrđivanje njihove efikasnosti i preciznosti u poređenju sa referentnom metodom koju preporučuju važeći standardi za elastomerne otisne materijale u stomatologiji (ISO 4823:2000, ANSI/ADA Specifikacija br.19). Za potrebe ovog istraživanja korišćeno je pet elastomernih otisnih materijala: dva kondenzaciona silikona (Oranwash L–Zhermack i Xantopren L blue–Heraeus Kulzer), dva adiciona silikona (Elite HD+ light body–Zhermack i Variotime Light Flow–Heraeus Kulzer) i jedan polietar (ImpregumTM Soft 3M ESPE). Uzorci ispitivanih otisnih materijala dobijeni su iz specijalne modle od nerđajućeg čelika koja je izrađena prema preporukama važećih standarda. Dimenzionalna stabilnost otisnih materijala ispitana je u zavisnosti od vremena (5min, 30min, 60min i 24h od momenta odvajanja otiska od modle), pri temperaturama od 23ºC, 35ºC i 40ºC, kao i pod uticajem različitih dezinficijenasa (5,25% NaOCl, glutaraldehid, benzalkonijum hlorid –Sterigum i sprej na bazi etanola i izopropanola – Zeta 7)...Dental impression materials are used to reproduce the form and relations of teeth and surrounding oral tissues, and the impressions are used for fabricating diagnostic and master casts. Dimensional stability of elastomeric impression materials under various conditions, is pivotal factor for the accuracy and durability of the final prosthetic restorations. It is defined as the ability of a material to retain its size and form over time. The aim of this study was to evaluate different possibilities of the original photometric methods in assessment of dimensional stability of elastomeric impression materials and to determine their efficiency and precision in comparison with the reference method recommended by the valid standards for dental elastomeric impression materials (ISO 4823:2000, ANSI/ADA Specification No.19). Five elastomeric impression materials were used in this study: two condensation silicones (Oranwash L - Zhermack and Xantopren L blue - Heraeus Kulzer), two addition silicones (Elite HD + light body - Zhermack and Variotime Light Flow - Heraeus Kulzer) and one polyether (ImpregumTM Soft 3M ESPE). A specific stainless steel test block, made according to the recommendations of ISO standard, was used for the fabrication of the samples of tested impression materials. Dimensional stability of the impression materials was examined as a function of time (5min, 30min, 1h and 24h after removal from the test block) at the temperatures of 23ºC, 35ºC and 40ºC. The effect of each applied disinfectant (5.25% NaOCl, glutaraldehyde, benzalkonium chloride – Sterigum and aerosol with ethanol and isopropanol - Zeta 7) was tested as well.

Evaluation of photometric methods in assessment of dimensional stability of elastomeric impression materials

U stomatologiji se otisni materijali upotrebljavaju za reprodukciju oblika i odnosa zuba i okolnih oralnih tkiva, a dobijeni otisci se koriste za izradu dijagnostičkih i master modela. Dimenzionalna stabilnost elastomernih otisnih materijala u različitim uslovima, važan je faktor koji direktno utiče na preciznost i trajnost indirektno izrađenih definitivnih zubnih nadoknada. Definiše se kao sposobnost materijala da zadrži svoju veličinu i oblik tokom vremena. Cilj ovog istraživanja je ispitivanje različitih mogućnosti originalnih fotometrijskih metoda u proceni dimenzionalne stabilnosti elastomernih otisnih materijala i utvrđivanje njihove efikasnosti i preciznosti u poređenju sa referentnom metodom koju preporučuju važeći standardi za elastomerne otisne materijale u stomatologiji (ISO 4823:2000, ANSI/ADA Specifikacija br.19). Za potrebe ovog istraživanja korišćeno je pet elastomernih otisnih materijala: dva kondenzaciona silikona (Oranwash L–Zhermack i Xantopren L blue–Heraeus Kulzer), dva adiciona silikona (Elite HD+ light body–Zhermack i Variotime Light Flow–Heraeus Kulzer) i jedan polietar (ImpregumTM Soft 3M ESPE). Uzorci ispitivanih otisnih materijala dobijeni su iz specijalne modle od nerđajućeg čelika koja je izrađena prema preporukama važećih standarda. Dimenzionalna stabilnost otisnih materijala ispitana je u zavisnosti od vremena (5min, 30min, 60min i 24h od momenta odvajanja otiska od modle), pri temperaturama od 23ºC, 35ºC i 40ºC, kao i pod uticajem različitih dezinficijenasa (5,25% NaOCl, glutaraldehid, benzalkonijum hlorid –Sterigum i sprej na bazi etanola i izopropanola – Zeta 7)...Dental impression materials are used to reproduce the form and relations of teeth and surrounding oral tissues, and the impressions are used for fabricating diagnostic and master casts. Dimensional stability of elastomeric impression materials under various conditions, is pivotal factor for the accuracy and durability of the final prosthetic restorations. It is defined as the ability of a material to retain its size and form over time. The aim of this study was to evaluate different possibilities of the original photometric methods in assessment of dimensional stability of elastomeric impression materials and to determine their efficiency and precision in comparison with the reference method recommended by the valid standards for dental elastomeric impression materials (ISO 4823:2000, ANSI/ADA Specification No.19). Five elastomeric impression materials were used in this study: two condensation silicones (Oranwash L - Zhermack and Xantopren L blue - Heraeus Kulzer), two addition silicones (Elite HD + light body - Zhermack and Variotime Light Flow - Heraeus Kulzer) and one polyether (ImpregumTM Soft 3M ESPE). A specific stainless steel test block, made according to the recommendations of ISO standard, was used for the fabrication of the samples of tested impression materials. Dimensional stability of the impression materials was examined as a function of time (5min, 30min, 1h and 24h after removal from the test block) at the temperatures of 23ºC, 35ºC and 40ºC. The effect of each applied disinfectant (5.25% NaOCl, glutaraldehyde, benzalkonium chloride – Sterigum and aerosol with ethanol and isopropanol - Zeta 7) was tested as well.

Toward mid-infrared nonlinear optics applications of silicon carbide microdisks engineered by lateral under-etching [invited]

We report the fabrication and characterization of silicon carbide microdisks on top of silicon pillars suited for applications from near-to mid-infrared. We probe 10 ?m diameter disks with different under-etching depths, from 4 ?m down to 1.4 ?m, fabricated by isotropic plasma etching and extract quality factors up to 8400 at telecom wavelength. Our geometry is suited to present high Q single-mode operation. We experimentally demonstrate high-order whispering-gallery mode suppression while preserving the fundamental gallery mode and investigate some requirements for nonlinear optics applications on this platform, specifically in terms of quality factor and dispersion for Kerr frequency comb generation

Mid-infrared ultra-short pulses nonlinear measurement of SiGe waveguides

International audienc

Dispersion engineered air-clad SiGe waveguides with low propagation loss in the mid-infrared

Summary form only given. Photonic devices operating in the mid-IR (3 μm to 13μm wavelength range) are of great interest for a wide range of applications, such as free-space communications, environmental monitoring or defence. Group IV-based material platforms [1], such as silicon-on-insulator (SOI)[2] and silicon-on-sapphire (SOS)[3] have attracted significant interest for mid-IR integrated photonics. However, absorption in silica beyond 3.5 μm and in sapphire beyond 5.5 μm eventually limits the operational wavelength band of these platforms. More recently, silicon-germanium (SiGe) alloys, with a transparency window potentially extending up to 13 μm depending on the Ge content [4] have emerged as an attractive alternative platform for mid-IR photonics [5-7]. In [6, 7] we reported Si 0.6 Ge 0.4 waveguides buried-in silicon with propagation loss of around 1dB/cm at 4μm, and nonlinear properties somewhat comparable to crystalline silicon between 3.5μm and 5μm

Mid-infrared supercontinuum generation in silicon-germanium all-normal dispersion waveguides

We demonstrate coherent supercontinuum generation spanning over an octave from a silicon germanium-on-silicon waveguide using ∼200fs pulses at a wavelength of 4 μm. The waveguide is engineered to provide low all-normal dispersion in the TM polarization. We validate the coherence of the generated supercontinuum via simulations, with a high degree of coherence across the entire spectrum. Such a generated supercontinuum could lend itself to pulse compression down to 22 fs.H2020 European Research Council (648546); Agence Nationale de la Recherche (ANR-17-CE24-0028)