FIG 1 - uploaded by Farsane Tabataba-Vakili
Content may be subject to copyright.
(a) Layer stack of the investigated sample grown on Si. (b) SEM image of a typical L3 cavity. The period a is 130 nm, the nominal r/a is 0.28, and the lateral holes of the L3 cavity are displaced by 0.10 a.
Source publication
III-nitride-on-silicon L3 photonic crystal cavities with resonances down to 315 nm and quality factors (Q) up to 1085 at 337 nm have been demonstrated. The reduction of the quality factor with decreasing wavelength is investigated. Besides the quantum well absorption below 340 nm, a noteworthy contribution is attributed to the residual absorption p...
Contexts in source publication
Context 1
... consists of a 50 nm AlN buffer layer and 5 GaN (1.2 nm)/ AlN (5 nm) quantum wells (QWs) emitting at a wavelength of 310 nm. The heterostructure is depicted in figure 1(a). Standard cleanroom processing is used to fabricate triangular lattice L3 photonic crystal cavities. ...
Context 2
... wells (QWs) or quantum dots (QDs)] are present. The investigated sample for photonic crystals was grown by ammonia molecu- lar beam epitaxy (MBE) on a standard Si (111) substrate. It consists of a 50 nm AlN buffer layer and 5 GaN (1.2 nm)/AlN (5 nm) quantum wells (QWs) emitting at a wavelength of 310 nm. The heterostructure is depicted in Fig. ...
Context 3
... after development by electron irradiation with a scan- ning electron microscope (SEM) (dose 65 C/m 2 ) for higher quality RIE of the SiO 2 mask. The Si substrate is then under- etched using XeF 2 gas, resulting in suspended air hole mem- branes. A scanning electron microscopy (SEM) image of a typical L3 cavity suspended membrane is shown in Fig. ...
Citations
... Numerous developments were dedicated to photonic crystal cavities as they can provide small mode volumes and a testbed for cavity quantum electrodynamics [107]. Despite the efforts provided by the community, the quality factors of two-dimensional photonic crystal cavities or one-dimensional nanobeam cavities have remained below their theoretical values [108][109][110][111][112][113][114][115][116][117][118][119][120]. It did not prevent reporting the demonstration of high-performance single devices from vertical-emitting photonic crystal lasers [121,122], watt-class photonic crystal lasers [123] or high-β values nanobeam lasers [124]. ...
The development of photonic platforms for the visible or ultra-violet spectral range represents a major challenge. In this article, we present an overview of the technological solutions available on the market. We discuss the pros and cons associated with heterogeneous or monolithic integration. We specifically focus on the III-nitride platform for integrated photonics. The III-nitrides offer every building block needed for a universal platform. We discuss the additional opportunities offered by combining III-nitride semiconductors with other materials such as two-dimensional materials.
... 34) Towards improvement of the Q-factors, fabrication methods have been studied for III-N semiconductor photonic crystal cavities. [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] One of the main difficulties arises from the high inertness of III-N semiconductors, which hinders undercut etching to form air-suspended photonic crystal cavity slabs by simple chemical etching. Among various undercut methods studied so far, bandgap selective photo-electrochemical (PEC) etching of InGaN-based sacrificial layers is a well-known method for the fabrication of GaN photonic crystal cavities. ...
GaN two-dimensional (2D) photonic crystal nanocavities with a single embedded InGaN quantum well are undercut by photo-electrochemical (PEC) etching and optically characterized to investigate the fundamental mode. The PEC etching selectively removes a InGaN-based sacrificial layer to form air-suspended GaN photonic crystal cavity slabs. We investigated the resonant modes of the photonic crystal nanocavities by micro-photoluminescence spectroscopy measurement at room temperature. The wavelengths of the measured resonant peaks and their dependence on the photonic crystal period agreed well with numerical analysis, allowing us to determine the fundamental mode in the measured spectra. The highest quality factor for the fundamental mode reached 3400 at blue wavelengths. This work would contribute to the improvement of GaN 2D photonic crystal nanocavities using PEC etching as well as their applications towards integrated light sources in visible wavelengths.
... Blue-UV Q comparison. Comparison of blue-UV resonator platforms[4][5][6][7][8][9][10][11][12]. The Si 3 N 4 µ ring Q at 405 nm is a conservative estimate based on loss. ...
We demonstrate a CMOS-foundry-based ${\rm{S}}{{\rm{i}}_3}{{\rm{N}}_4}$ S i 3 N 4 photonic platform at blue and violet wavelengths that exhibits record-high intrinsic Qs of around 6 M at 453 nm and ${\lt}{{1}}\;{\rm{dB/cm}}$ < 1 d B / c m waveguide propagation loss of around 405 nm.
... The main limitations for the Q factor at short wavelength are scattering loss, which scales with λ −2 due to sidewall roughness, as well as surface absorption [36]. At λ = 420 nm, we estimate Q abs,QW = 5000 in analogy to Ref. [192] (see chapter 4). At longer wavelength, the QW absorption vanishes, as well as its contribution to Q load . ...
... Low threshold energies of 1.7 mJ · cm −2 per pulse (425 kW · cm −2 peak power) at the critical coupling gap and 1.2 mJ · cm −2 per pulse (300 kW · cm −2 ) in the under-coupled regime were observed. Large [192] and [201]. This chapter covers: ...
III-nitride semiconductors (AlN, GaN, InN and their alloys) have become an integral part of our daily lives as they are used in white, blue, green, and ultraviolet light emitting diodes, as well as laser diodes and power and high frequency electronics. This material is highly versatile due to its tuneable large direct band gap from the ultraviolet to the visible. III-nitrides give access to a very wide range of electronic, optoelectronic, and photonic applications. In photonics, a promising field relies on the III-nitride on silicon platform for next generation photonic integrated circuits due to its large transparency window from the ultraviolet to the near-infrared and the possibility of monolithic integration of active emitters such as quantum wells and quantum dots. In this thesis, we study different photonic devices and their integration into active and passive photonic circuits at wavelengths going from the ultraviolet to the near-infrared. We demonstrate low threshold pulsed optically pumped lasing and the first active microlaser photonic circuits in the blue and ultraviolet spectral ranges. We also propose a scheme for electrical injection in microrings that is compatible with photonic circuits and investigate III-nitrides bonded on SiO₂ as a platform for passive photonic circuits in the near-infrared.
... However, later reports mostly relied directly on 3D-FDTD simulations thanks to the large increase in computational capabilities [18,31,60]. In any case, the computed Q th values for III-N PhC membrane nanocavities always outperform experimental values [12,13,18,47,[68][69][70][71] even in the case of high-Q NIR 1D-PhC AlN nanobeam cavities (Figure 9) [49], so that its weight is often discarded when evaluating Q exp . ...
Owing to their wide direct bandgap tunability, III-nitride (III-N) compound semiconductors have been proven instrumental in the development of blue light-emitting diodes that led to the so-called solid-state lighting revolution and blue laser diodes that are used for optical data storage. Beyond such conventional optoelectronic devices, in this review, we explore the progress made in the past 15 years with this low refractive index material family for the realization of microdisks as well as 2D and 1D photonic crystal (PhC) membrane cavities. Critical aspects related to their design and fabrication are first highlighted. Then, the optical properties of passive PhC structures designed for near-infrared such as their quality factor and their mode volume are addressed. Additional challenges dealing with fabrication pertaining to structures designed for shorter wavelengths, namely the visible to ultraviolet spectral range, are also critically reviewed and analyzed. Various applications ranging from second and third harmonic generation to microlasers and nanolasers are then discussed. Finally, forthcoming challenges and novel fields of application of III-N photonic cavities are commented.
... The main limitation for the Q factor at short wavelength are scattering losses that scale with λ −4 due to sidewall roughness. At λ = 420 nm we estimate Q abs,QW = 5000 in analogy to ref. 35 . At longer wavelength, the quantum well absorption vanishes as well as its contribution to Q loaded . ...
On-chip microlaser sources in the blue constitute an important building block for complex integrated photonic circuits on silicon. We have developed photonic circuits operating in the blue spectral range based on microdisks and bus waveguides in III-nitride on silicon. We report on the interplay between microdisk-waveguide coupling and its optical properties. We observe critical coupling and phase matching, i.e. the most efficient energy transfer scheme, for very short gap sizes and thin waveguides (g = 45 nm and w = 170 nm) in the spontaneous emission regime. Whispering gallery mode lasing is demonstrated for a wide range of parameters with a strong dependence of the threshold on the loaded quality factor. We show the dependence and high sensitivity of the output signal on the coupling. Lastly, we observe the impact of processing on the tuning of mode resonances due to the very short coupling distances. Such small footprint on-chip integrated microlasers providing maximum energy transfer into a photonic circuit have important potential applications for visible-light communication and lab-on-chip bio-sensors.
... An extensive range of enhanced and unusual optical properties, including dynamically tuneable/switchable and nonlinear functionalities, have been demonstrated at technologically important near-infrared and visible frequencies in metamaterials and metasurfaces comprised of nanostructured plasmonic metals (very typically gold), high-index dielectrics (often silicon [38,154,[167][168][169], but also GaAs [170], germanium [171], perovskites [118] and chalcogenides [22,66]) and metal/dielectric composites. However, while the ultraviolet (UV) and short-wavelength, high-energy visible (HEV) spectral range is of considerable interest and importance to a variety of applications in the physical, environmental, manufacturing and bio-sciences [172][173][174][175][176][177][178][179][180], it is less often the focus of attention in metamaterials research than the longer-wavelength visible / near-infrared domain. A significant factor in this, aside from dimensional requirements/constraints on nanofabrication for shorter wavelengths, is the fact that the aforementioned archetypal material platforms (gold and silicon) are unsuitable in the UV-HEV band. ...
Photonic metamaterials - media artificially structured at the nanometre scale - provide extraordinary optical properties not found in nature. In this work I explored opportunities provided by changes of complex optical properties of chalcogenide alloys related to compositional variation and structural phase change to develop switchable and tunable plasmonic and dielectric metamaterials:
• I have systematically explored the properties of Bi:Sb:Te across UV to near infrared wavelengths through combinatorial high-throughput mapping techniques for the widest compositional spread reported so far. This study reveals that Bi:Sb:Te has better plasmonic properties than gold at wavelengths below 580 nm and silver below 365 nm; ability to support dielectric (Mie) resonances better than oxides at telecommunication wavelengths beyond 1200 nm; epsilon-near-zero properties across UV to IR wavelengths; sub-unity refractive index (down to 0.7) in the UV and the highest refractive index in the near-IR (up to 11.5 at 1680 nm) reported so far to our knowledge.
• I have studied for the first time the plasmonic character of amorphous Bi:Te and developed resonant optical metasurfaces based on this alloy that present strong, period-dependent plasmonic absorption resonances (QMax = 7.5) in the visible range. Furthermore, I have investigated changes of optical properties of this alloy upon structural phase change from amorphous to crystalline phases.
• I have studied for the first time channelling of light through nano-hole arrays filled with dispersive low-epsilon chalcogenides. The complex changes in the composite’s spectral response depend strongly on the interplay between the dispersion of the optical properties of the plasmonic nanostructure and the low-epsilon medium and lead to increase of transmission over a broad range of plasmonic frequencies.
• I have developed the first switchable UV metamaterials that exploits the low refractive index (equal to 1.07 at 245 nm for c-GST) and phase change properties of chalcogenides. In particular, I have shown that laser-induced structural phase transitions can be used to switch quality factors of dielectric resonances (QMax = 15) in metamaterials without affecting their spectral positions.
... In the telecom band, a high Q int of up to 2.5 × 10 6 has been recorded in crystalline AlN microrings [17], yielding nonlinear photonic devices such as broadband Kerr frequency combs [18] and high-efficiency Raman lasers [19]. Nonetheless, the current Q-factors of ∼1.1 k-7.3 k recorded in crystalline AlN-based UV resonators at 310-411 nm [20][21][22][23][24] are far from the maximum attainable Q-factors as limited by the Rayleigh scattering loss (∝ λ −4 ). ...
... [23] [21] [20] [22] AlN μRing AlN μDisk AlN PhC-cavity Q int Wavelength (nm) [15] This work [24] ...
Development of low-loss photonic components in the ultraviolet (UV) band will open new prospects for classical and quantum optics. Compared with other integrated platforms, aluminum nitride (AlN) is particularly attractive as it features an enormous bandgap of ∼ 6.2 eV and intrinsic χ ( 2 ) and χ ( 3 ) susceptibilities. In this work, we demonstrate a record quality factor of 2.1 × 10 5 (optical loss ∼ 8 dB / cm ) at 390 nm based on single-crystalline AlN microrings. The low-loss AlN waveguide represents a significant milestone toward UV photonic integrated circuits as it features full compatibility for future incorporation of AlGaN-based UV emitters and receivers. On-chip UV spectroscopy, nonlinear optics, and quantum information processing can also be envisioned.
... Modes on the high energy side of the QW peak diminish in relative intensity and broaden, likely due to absorption in the QW shifted by the quantum-confined Stark effect. 23,25 For a disk radius R ¼ 1.5 lm and effective refractive index n eff ¼ 2.1, the free spectral range is k 2 /2pRn eff , approximately 64 meV (10 nm) at 2.8 eV/440 nm. Therefore, the high peak density can be attributed to two factors: the small silicon post diameter resulting in modes with multiple radial nodes and the large relative thickness of the epilayers ($3k/n eff ), resulting in modes with multiple vertical nodes. ...
III-nitride surface states are expected to impact high surface-to-volume ratio devices, such as nano- and micro-wire light-emitting diodes, transistors, and photonic integrated circuits. In this work, reversible photoinduced oxygen desorption from III-nitride microdisk resonator surfaces is shown to increase optical attenuation of whispering gallery modes by 100 cm⁻¹ at λ = 450 nm. Comparison of photoinduced oxygen desorption in unintentionally and n⁺-doped microdisks suggests that the spectral changes originate from the unpinning of the surface Fermi level, likely taking place at etched nonpolar III-nitride sidewalls. An oxygen-rich surface prepared by thermal annealing results in a broadband Q improvement to state-of-the-art values exceeding 1 × 10⁴ at 2.6 eV. Such findings emphasize the importance of optically active surface states and their passivation for future nanoscale III-nitride optoelectronic and photonic devices.
Photonic materials with tuneable and switchable ultraviolet (UV) to high-energy-visible (HEV) optical properties would benefit applications in sensing, high-density optical memory, beam-steering, adaptive optics and light modulation. Here, for the first time, we demonstrate a non-volatile switchable dielectric metamaterial operating in the UV-HEV spectral range. Nano-grating metamaterials in a layered composite of low-loss ZnS/SiO2 and the chalcogenide phase-change medium germanium antimony telluride (Ge2Sb2Te5) exhibit reflection resonances at UV-HEV wavelengths that are substantially modified by light-induced (amorphous-crystalline) phase transitions in the chalcogenide layer. Despite the presence of the lossy GST, resonance quality factors up to Q~15 are ensured by the transparency (low losses) of ZnS/SiO2 in the UV-HEV spectral range and values of Q increase as the refractive index of Ge2Sb2Te5 decreases, upon crystallization. Notably however, this switching leaves resonance spectral positions unchanged.
