Search query: ,Solid immersion lens．enhanced nano． photoluminescence：

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abstract: We demonstrate a far field nano photoluminescence setup based on the combination of a hemispherical solid immersion lens (SIL) with a confocal microscope. The spatial resolution is confirmed to be 0.4 times the wavelength in vacuum in terms of half width at half maximum. The collection efficiency is found to be about five times higher than the same microscope without SIL, which is consistent with our theoretical analysis. We investigate in detail the influence of an air gap between the SIL and the sample surface on the system performance, and prove both experimentally and theoretically the tolerance of this far field system to an air gap of several micrometers. These features make the present setup an ideal system for spatially resolved spectroscopy of semiconductor nanostructures. In particular, we show two examples of such applications in which the present setup is clearly suitable: Studies of excitonic transport in quantum wells and spectroscopy of single quantum dots with emphasis on polarization depe.
author_names: Sebastian Moehl

Hui Zhao

B Dal Don

Sven Wachter

Heinz Kalt
title: Solid immersion lens enhanced nano photoluminescence: Principle and applications
year: 2003

abstract: We investigate the in plane transport of excitons in quantum wells by nano photoluminescence. The experimental method is based on a confocal microscope with an enhanced resolution given by the introduction of a solid immersion lens. In combination with pulsed laser excitation and streak camera detection, we have access to transport phenomena on a timescale faster than the time of scattering with acoustic phonons and a length scale of the light wavelength. We use ZnSe based quantum wells as a model system since hot excitons with well defined excess energy can be formed assisted by the emission of optical phonons. This results e.g. in a periodic quenching of the excitonic transport length as function of excitation excess energy which, in comparison, is not found in GaAs quantum wells. Monte Carlo simulations of the nonlinear expansion of the luminescence spot observed as a function of time reveal the difference between the spatial profiles of the luminescence and the exciton density. The latter shows an oscillatory behaviour in time due to the dominant backscattering, when the first acoustic phonon is emitted. From this oscillation we can determine simultaneously the coherence time and length of the excitonic transport in ZnSe quantum wells. (c) 2004 WILEY VCH Verlag GmbH Co. KGaA, Weinheim)
author_names: B Dal Don

Hui Zhao

Gregor Schwartz

Thomas Unkelbach

Heinz Kalt
title: Coherence length and time of excitons in ZnSe quantum wells
year: 2004

abstract: We report investigations on excitonic transport in ZnSe quantum wells using far field nano photoluminescence enhanced by a solid immersion lens. The 250 nm spatial resolution and 5 ps temporal resolution allow the access to non classical transport regimes. From zero phonon line spectroscopy we deduce the spatial distribution of the PL intensity under different cw excitation condition and its temporal evolution after a pulsed excitation, respectively. The periodic quenching of the transport length as function of excitation excess energy and the nonlinear expansion of the PL spot observed in time resolved experiments reveal the dominance of hot exciton effects. The experimental data are well modelled by a Monte Carlo simulation. Spatially resolved phonon sideband spectroscopy is used to observe directly the coherent transport and the energy relaxation of hot excitons during transport. The coherence length is measured to be 300 400 nm at low temperatures and the excitons are found to remain hot during transport on a length scale of several micrometers.
author_names: Hui Zhao

B Dal Don

Sebastian Moehl

Heinz Kalt
title: Non classical excitonic transport in quantum wells
year: 2003

abstract: We have discussed the resolution of submicron photoluminescence (PL) imaging using a solid immersion lens (SIL) which collects an evanescent light field. We apply the SIL microscope to measure PL image of a strip line patterned GaAs quantum well structure at low temperature. An improved resolution beyond diffraction limit and high collection efficiency of PL are realized.
author_names: Motoyoshi Baba

Masahiro Yoshita

Takeaki Sasaki

Hidefumi Akiyama
title: Application of Solid Immersion Lens to Submicron Resolution Imaging of Nano Scale Quantum Wells
year: 1999

abstract: Summary form only given. The solid immersion lens (SIL) is an aberration free solid lens of high refractive index material with a truncated sphere shape. Combining the SIL with a standard optical microscope, PL imaging with high spatial resolution and high collection efficiency was demonstrated. In this work we applied the SIL to microscopic photoluminescence (micro PL) spectroscopy and imaging to characterize local electronic properties and real space carrier migration of sub /spl mu/m scale in facet growth GaAs quantum well (QW) structures.
author_names: Masahiro Yoshita

Motoyoshi Baba

Hidefumi Akiyama
title: Solid immersion photoluminescence imaging and spectroscopy with high spatial resolution on GaAs nano
year: 1999

abstract: By solid immersion photoluminescence imaging and spectroscopy, the spatial distribution of electronic states and carrier distribution and flow in GaAs facet growth nano structures and [110] quantum wells can been revealed with high spatial resolution of sub /spl mu/m scale.
author_names: Masahiro Yoshita

Hidefumi Akiyama
title: Solid immersion photoluminescence microscopy of novel GaAs nano structures
venue: Technical Digest. CLEO/Pacific Rim 2001. 4th Pacific Rim Conference on Lasers and Electro Optics (Cat. No.01TH8557)
year: 2001

abstract: Bright single photon sources are an essential ingredient for quantum technology applications. Solid state single photon emitters are particularly suitable for the integration in on chip devices [1] However, they suffer from poor extraction efficiencies due to the high refractive index contrast between the bulk semiconductor and air, resulting in a small fraction of the emitted light being collected in free space. Several approaches to increase the extraction of light from semiconductor emitters have been implemented, including optical cavities (such as micro pillars, nanowires, and gratings) and solid immersion lenses [2] Here we report on a different approach that makes use of metallic nano rings that act as local lenses that focus the laser excitation and increase the intensity of the collected light. Such an effect is validated by finite difference time domain simulations, that we use to optimise the ring dimensions. The position of the emitters is measured with respect to alignment markers with accuracies of ~25 nm, via a photoluminescence imaging technique [3] (see Fig. 1a) Rings of inner diameter of ~440 nm are deposited on the sample surface (Fig. 1b) by means of electron beam lithography, Cr/Au deposition and chemical lift off, and centred in correspondence to single epitaxial InAs/GaAs quantum dots (QDs) The emission intensity collected from the same QD before and after ring deposition is shown in Fig 1c: the ring allows enhancements of up to a factor 25 in the intensity of single QD emission lines [4] Such ring device is scalable, simple to fabricate and broadband, compatible with any substrate and emitter, including room temperature light sources such as colloidal QDs, defect centres in diamond and in two dimensional materials.
author_names: Oliver Joe Trojak

Luca Sapienza

Jin Dong Song
title: Broadband emission enhancement of the extraction of light from solid state emitters by metallic nano rings
year: 2017

abstract: We report on the enhancement of the collection efficiency from epitaxial InAs/GaAs quantum dots through the deposition of metallic rings centered around single emitters, located with a nanometer scale accurate photoluminescence imaging technique. Increases of up to x17 in the brightness of the single photon emission are measured, due to an excitation and collection lensing effect. Furthermore, we demonstrate efficient confinement of visible light in disordered photonic crystal waveguides, reaching quality factors of ~10000, exceeding values previously reported in two dimensional photonic crystals. Bright single photon sources are required for various quantum information technology applications. However, the photon extraction efficiency from solid state emitters can be severely limited by the high refractive index mismatch between semiconductors (like GaAs) and air, resulting in most of the emitted light being trapped within the high index material. Several approaches have been implemented in order to increase the extraction efficiency, including photonic nanowires, micropillars and circular gratings. Solid immersion lenses, deposited on the materials surface or 3D printed via in situ lithography, have also been used to focus the excitation and the emitted light, thus increasing the emitted photon flux. We report on two different approaches that we follow to control the light matter interaction on a chip, based on broadband metallic rings and high quality light confinement in disordered photonic crystal waveguides. By implementing a photoluminescence imaging technique, we position single InAs/GaAs quantum dots grown by molecular beam epitaxy with accuracies of ~20 nm. We then deposit, by means of electron beam lithography followed by a lift off, metallic gold rings with inner diameter of ~440 nm, centered around single emitters (see Fig.1a) A confocal photoluminescence set up is used to excite selected single quantum dots with a continuous wave laser and the intensity of the single photon emission is measured on a charge coupled device (CCD) before and after the rings are deposited. (a) (b) Fig.1: (a) Scanning electron microscope image of a gold ring deposited on a GaAs chip containing InAs quantum dots. (b) Photoluminescence spectra measured from a single quantum dot, before (red) and after (blue) metallic ring deposition (temperature T 10K, laser excitation wavelength 780 nm) We measure enhancements of the emission intensity as high as ~17 (see Fig.1b) due to a lensing effect on the laser excitation light and on the emitted light. Compared to optical cavities, our ring devices are intrinsically broadband, since they do not rely on a high quality factor photonic cavity, and can therefore be implemented with any kind of solid state emitter. The performances of the rings, obtained with a much easier fabrication technique compared to in situ lithography, also surpass those of 3D printed solid immersion lenses by almost an order of magnitude. Given the dimensions in play, such metallic rings could also be fabricated using lower resolution techniques such as photolithography and nano imprinting, thus improving scalability. A variety of solid state emitters like colloidal quantum dots, defect centers in diamond and in two dimensional materials act as single photon sources operating in the visible range of wavelengths. Being able to control the spontaneous emission dynamics and efficiently confine the emitted light in high quality optical cavities is of paramount importance for the implementation of visible emitters in quantum photonic devices. However, the quality factors of visible light confinement on a chip so far reported in highly engineered photonic crystal cavities lie between a few hundreds and a few thousands: the enhancement of the light matter interaction achievable is therefore limited compared to devices operating at longer wavelengths. By using disorder as a resource, we demonstrate an improvement in the quality of light confinement on a chip of up to an order of magnitude, in optical cavities operating in the Anderson localized regime (see Fig.2) We report quality factors reaching values of ~10000 in disordered photonic crystal waveguides operating in the visible range of wavelengths on a silicon nitride platform. This is a significant improvement with respect to the state of the art and proves the potential of disorder induced confinement of visible light for on chip photonics. Fig.2: Photoluminescence spectrum of an Anderson localized cavity (symbols) and its Lorentzian fit (dashed line) showing a quality factor Q 9300+ 800 (temperature T 300K, laser excitation wavelength 473 nm) REFERENCES 1. Claudon, J. et al. "A highly efficient single photon source based on a quantum dot in a photonic nanowire," Nature Photonics, Vol. 4, 174 177, 2010. 2. Somaschi, N. et al. "Near optimal single photon sources in the solid state" Nature Photonics, Vol. 10, 340 345, 2016. 3. Davanco, M. et al. "A circular dielectric grating for vertical extraction of single quantum dot emission" Applied Physics Letters, Vol. 99, 041102, 2011. 4. Serrels, K.A. et al. "Solid immersion lens applications for nanophotonic devices" Journal of Nanophotonics, Vol. 2, 021854, 2008. 5. Sartison, M. et al. "Combining in situ lithography with 3D printed solid immersion lenses for single quantum dot spectroscopy" Scientific Reports, Vol. 7, 39916, 2017. 6. Sapienza, L. et al. "Nanoscale optical positioning of single quantum dots for bright and pure single photon emission" Nature Communications, Vol. 7, 7833, 2015. 7. Crane, T. O.J. Trojak, L. Sapienza, "Anderson localization of visible light" https:/arxiv.org/abs/1605.08614v2, 2016.
author_names: Oliver Joe Trojak

Tom Crane

Jin Dong Song

Luca Sapienza
title: Nano rings for improved extraction of single photons and disorder induced efficient visible light confinement on a chip
year: 2017

abstract: CaB2O4 powders and ceramics were prepared by the conventional solid state reaction. In vitro hydroxyapatite (HA) mineralization was investigated by soaking the samples in simulated body fluid (SBF) for various time periods. X ray diffraction and structural refinements, scanning electron microscopy and X ray energy dispersive spectra measurements were applied to investigate apatite formation before and after immersion in SBF. HA can easily form flower like nanostructures with nano needles even when soaked in SBF for several hours. The in vitro bioactivity of CaB2O4 was attributed to easy formation of B OH groups in the CaB2O4 structure when soaked in SBF solutions. In the process of mineralization, the luminescence evolution of Eu3+ ions, a well known structural probe, was detected by photoluminescence spectra and photoluminescence decay curves. This suggested that the process of mineralization can be monitored by the luminescence intensity of Eu3+ ions in the mineralization products. The current study will open up a new and simple in vivo avenue for in situ monitoring of hydroxyapatite conversion using a fiber luminescence spectrometer.
author_names: Shuyun Qi

Yanlin Huang

Yadong Li

Peiqing Cai

Sun Il Kim

Hyo Jin Seo
title: Probe spectrum measurements of Eu3+ ions as a relevant tool for monitoring in vitro hydroxyapatite formation in a new borate biomaterial.
venue: Journal of materials chemistry. B
year: 2014

abstract: In this thesis I present my research on nano scale light control using several novel approaches. I have demonstrated a planar metal nano structure with cylindrical symmetry that is designed to create a super oscillation of electromagnetic waves to focus light down to sizes smaller than the Abbe diffraction limit. For the first time this super oscillatory lens was experimentally used for imaging of nano structures. A pair of 0.3 lambda diameter nano holes with 0.16 lambda edge to edge separation were resolved. I have demonstrated a novel type of super oscillatory lens which produces a continuous distribution of sub wavelength light localisations extending over several wavelengths along the optical axis. This 'optical needle' is also characterised by a large field of view. I have experimentally demonstrated a optical needle lens with 7um depth of focus and 16% narrower than a diffraction limited focal spot. I have characterised the point spread function of the above mentioned super oscillatory lenses, i.e. their ability to accurately image a point source. The images of the point source generated by these super oscillatory lenses are at least 24% smaller than that produced by an ideal glass lens restrained by the Abbe diffraction limit. I have experimentally verified the imaging characteristics of the optical needle lens and demonstrated its ability to detect the off axis placement of a point like source. I have developed the nano fabrication processes for manufacturing the super oscillatory lenses on thin films of metals (Au, Al, Ti) using gallium focused ion beam milling technology. The focusing characteristics of the fabricated structures showed very good agreement with computational predictions. I have computationally shown that objects placed within the field of viewfocfocus of the optical needle lens can be imaged with super resolution quality. This is a significant improvement over the sub wavelength step scanning imaging technique reported in this thesis for the other kind of super oscillatory lens. For example, a super oscillatory lens can resolve a 'random' cluster of 0.15 lambda diameter nano holes with the smallest edge to edge separation of 0.28 lambda. I have experimentally demonstrated the first prototype of a solid immersion superoscillatory lens that promises to achieve a 50 nm hotspot with 405 nm illumination for applications in heat assisted magnetic recording technology. I have demonstrated for the first time a planar diffraction grating for visible light designed by arranging meta molecules to produce a periodic phase ramp. I have also demonstrated the first ever metamaterial based planar lens array that produced a 2D array of sub wavelength foci. Finally, I have provided the first experimental evidence that photoluminescence of gold can be substantially enhanced by patterning the film with designed 2D nano structured array (or, metamaterials) When resonant two photon excitation is used the metamaterial enhances the photoluminescence by more than 76 times. I have also observed that the photoluminescence emission peaks are linked to the frequencies of absorption resonances in the metamaterials.
author_names: Tapashree Roy
title: Control and localisation of light with engineered nano structures
year: 2014