1
|
Azzam SI, Kildishev AV, Ma RM, Ning CZ, Oulton R, Shalaev VM, Stockman MI, Xu JL, Zhang X. Ten years of spasers and plasmonic nanolasers. LIGHT, SCIENCE & APPLICATIONS 2020; 9:90. [PMID: 32509297 PMCID: PMC7248101 DOI: 10.1038/s41377-020-0319-7] [Citation(s) in RCA: 65] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 04/15/2020] [Accepted: 04/17/2020] [Indexed: 05/25/2023]
Abstract
Ten years ago, three teams experimentally demonstrated the first spasers, or plasmonic nanolasers, after the spaser concept was first proposed theoretically in 2003. An overview of the significant progress achieved over the last 10 years is presented here, together with the original context of and motivations for this research. After a general introduction, we first summarize the fundamental properties of spasers and discuss the major motivations that led to the first demonstrations of spasers and nanolasers. This is followed by an overview of crucial technological progress, including lasing threshold reduction, dynamic modulation, room-temperature operation, electrical injection, the control and improvement of spasers, the array operation of spasers, and selected applications of single-particle spasers. Research prospects are presented in relation to several directions of development, including further miniaturization, the relationship with Bose-Einstein condensation, novel spaser-based interconnects, and other features of spasers and plasmonic lasers that have yet to be realized or challenges that are still to be overcome.
Collapse
Affiliation(s)
- Shaimaa I. Azzam
- School of Electrical & Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907 USA
- Purdue Quantum Science and Engineering Institute, Purdue University, West Lafayette, IN 47907 USA
| | - Alexander V. Kildishev
- School of Electrical & Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907 USA
- Purdue Quantum Science and Engineering Institute, Purdue University, West Lafayette, IN 47907 USA
| | - Ren-Min Ma
- State Key Lab for Mesoscopic Physics and School of Physics, Peking University, Beijing, China
- Frontiers Science Center for Nano-optoelectronics & Collaborative Innovation Center of Quantum Matter, Beijing, China
| | - Cun-Zheng Ning
- Department of Electronic Engineering and International Center for Nano-Optoelectronics, Tsinghua University, 100084 Beijing, China
- School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, AZ 85287 USA
| | - Rupert Oulton
- The Blackett Laboratory, Imperial College London, South Kensington, London, SW7 2AZ UK
| | - Vladimir M. Shalaev
- School of Electrical & Computer Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907 USA
- Purdue Quantum Science and Engineering Institute, Purdue University, West Lafayette, IN 47907 USA
| | - Mark I. Stockman
- Center for Nano-Optics (CeNO) and Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303 USA
| | - Jia-Lu Xu
- Department of Electronic Engineering and International Center for Nano-Optoelectronics, Tsinghua University, 100084 Beijing, China
| | - Xiang Zhang
- Nanoscale Science and Engineering Center, University of California, Berkeley, Berkeley, CA 94720 USA
- Faculties of Sciences and Engineering, University of Hong Kong, Hong Kong, China
| |
Collapse
|
2
|
Xiao K, Pettit RM, Ge W, Nguyen LH, Dadras S, Vamivakas AN, Bhattacharya M. Higher order correlations in a levitated nanoparticle phonon laser. OPTICS EXPRESS 2020; 28:4234-4248. [PMID: 32122080 DOI: 10.1364/oe.384417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 01/20/2020] [Indexed: 06/10/2023]
Abstract
We present theoretical and experimental investigations of higher order correlations of mechanical motion in the recently demonstrated optical tweezer phonon laser, consisting of a silica nanosphere trapped in vacuum by a tightly focused optical beam [R. M. Pettit et al., Nature Photonics 13, 402 (2019)]. The nanoparticle phonon number probability distribution is modeled with the master equation formalism in order to study its evolution across the lasing threshold. Up to fourth-order equal-time correlation functions are then derived from the probability distribution. Subsequently, the master equation is transformed into a nonlinear quantum Langevin equation for the trapped particle's position. This equation yields the non-equal-time correlations, also up to fourth order. Finally, we present experimental measurements of the phononic correlation functions, which are in good agreement with our theoretical predictions. We also compare the experimental data to existing analytical Ginzburg-Landau theory where we find only a partial match.
Collapse
|
3
|
Wollman EE, Verma VB, Lita AE, Farr WH, Shaw MD, Mirin RP, Woo Nam S. Kilopixel array of superconducting nanowire single-photon detectors. OPTICS EXPRESS 2019; 27:35279-35289. [PMID: 31878700 DOI: 10.1364/oe.27.035279] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 10/18/2019] [Indexed: 06/10/2023]
Abstract
We present a 1024-element near-infrared imaging array of superconducting nanowire single photon detectors (SNSPDs) using a 32×32 row-column multiplexing architecture. The array has an active area of 0.96 × 0.96 mm, making it the largest SNSPD array reported to date in terms of both active area and pixel count. Using a 64-channel time-tagging readout, we have characterized the array's yield, efficiency, and timing resolution. Large arrays of SNSPDs are desirable for applications such as imaging, spectroscopy, or particle detection.
Collapse
|
4
|
Lüders C, Thewes J, Assmann M. Real time g (2) monitoring with 100 kHz sampling rate. OPTICS EXPRESS 2018; 26:24854-24863. [PMID: 30469596 DOI: 10.1364/oe.26.024854] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 07/14/2018] [Indexed: 06/09/2023]
Abstract
We introduce a technique to determine photon correlations of optical light fields in real time. The method is based on ultrafast phase-randomized homodyne detection and allows us to follow the temporal evolution of the second-order correlation function g(2)(0) of a light field. We demonstrate the capabilities of our approach by applying it to a laser diode operated in the threshold region. In particular, we are able to monitor the emission dynamics of the diode switching back and forth between lasing and spontaneous emission with a g(2)(0)-sampling rate of 100 kHz.
Collapse
|
5
|
Chen L, Schwarzer D, Verma VB, Stevens MJ, Marsili F, Mirin RP, Nam SW, Wodtke AM. Mid-infrared Laser-Induced Fluorescence with Nanosecond Time Resolution Using a Superconducting Nanowire Single-Photon Detector: New Technology for Molecular Science. Acc Chem Res 2017; 50:1400-1409. [PMID: 28573866 DOI: 10.1021/acs.accounts.7b00071] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In contrast to UV photomultiplier tubes that are widely used in physical chemistry, mid-infrared detectors are notorious for poor sensitivity and slow time response. This helps explain why, despite the importance of infrared spectroscopy in molecular science, mid-infrared fluorescence is not more widely used. In recent years, several new technologies have been developed that open new experimental possibilities for research in the mid-infrared. In this Account, we present one of the more promising technologies, superconducting nanowire single photon detectors (SNSPDs) by sharing our experience with its use in a typical experiment carried out by physical chemists (laser-induced fluorescence) and comparing the SNSPD to a detector commonly used by physical chemists (InSb at LN Temperature). SNSPDs are fabricated from a thin film of superconducting metal, patterned into a meandering nanowire. The nanowire is cooled below its superconducting temperature, Tc, and held in a constant current circuit below the critical current necessary to destroy superconductivity, Ic. Upon absorption of a photon, the resulting heat is sufficient to destroy superconductivity across the entire width of the nanowire, an event that can be detected as a voltage pulse. In contrast to semiconductor-based detectors, which have a long wavelength cutoff determined by the band gap, the SNSPD exhibits single-photon sensitivity across the entire mid-IR spectrum. As these devices have not been used extensively outside the field of light detection technology research, one important goal of this Account is to provide practical details for the implementation of these devices in a physical chemistry laboratory. We provide extensive Supporting Information describing what is needed. This includes information on a liquid nitrogen cooled monochromator, the optical collection system including mid-infrared fibers, as well as a closed-cycle cryogenic cooler that reaches 0.3 K. We demonstrate the advantages of these detectors in a time-resolved laser-induced infrared fluorescence experiment on the energy pooling in crystalline CO overlayers formed on a NaCl(100) surface. We present dispersed fluorescence spectra recorded from 1.9 to 7.0 μm obtained by single-photon counting. We also estimate the sensitivity of this WSi-based detection system at 3 μm; the system's noise equivalent power (NEP) value is ∼10-3 of a conventional InSb photovoltaic device. Straightforward modifications are expected to provide another 100 000-fold improvement. We demonstrate that the temporal resolution of the experiment is limited only by the pulse duration of the laser used in this work (fwhm = 3.7 ns). The use of SNSPDs enables dramatically improved observations of energy pooling in cryogenic molecular crystals.
Collapse
Affiliation(s)
- Li Chen
- Department
of Dynamics at Surfaces, Max Planck Institute for Biophysical Chemistry, Göttingen 37077, Germany
| | - Dirk Schwarzer
- Department
of Dynamics at Surfaces, Max Planck Institute for Biophysical Chemistry, Göttingen 37077, Germany
| | - Varun B. Verma
- National Institute of Standards and Technology, Boulder, Colorado 80305, United States
| | - Martin J. Stevens
- National Institute of Standards and Technology, Boulder, Colorado 80305, United States
| | - Francesco Marsili
- National Institute of Standards and Technology, Boulder, Colorado 80305, United States
| | - Richard P. Mirin
- National Institute of Standards and Technology, Boulder, Colorado 80305, United States
| | - Sae Woo Nam
- National Institute of Standards and Technology, Boulder, Colorado 80305, United States
| | - Alec M. Wodtke
- Department
of Dynamics at Surfaces, Max Planck Institute for Biophysical Chemistry, Göttingen 37077, Germany
| |
Collapse
|
6
|
Kuhn S, Hartmann S, Elsäßer W. Photon-statistics-based classical ghost imaging with one single detector. OPTICS LETTERS 2016; 41:2863-2866. [PMID: 27304308 DOI: 10.1364/ol.41.002863] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We demonstrate a novel ghost imaging (GI) scheme based on one single-photon-counting detector with subsequent photon statistics analysis. The key idea is that instead of measuring correlations between the object and reference beams such as in standard GI schemes, the light of the two beams is superimposed. The photon statistics analysis of this mixed light allows us to determine the photon number distribution as well as to calculate the central second-order correlation coefficient. The image information is obtained as a function of the spatial resolution of the reference beam. The performance of this photon-statistics-based GI system with one single detector (PS-GI) is investigated in terms of visibility and resolution. Finally, the knowledge of the complete photon statistics allows easy access to higher correlation coefficients such that we are able to perform here third- and fourth-order GI. The PS-GI concept can be seen as a complement to already existing GI technologies thus enabling a broader dissemination of GI as a superior metrology technique, paving the road for new applications in particular with advanced photon counting detectors.
Collapse
|
7
|
Verma VB, Korzh B, Bussières F, Horansky RD, Dyer SD, Lita AE, Vayshenker I, Marsili F, Shaw MD, Zbinden H, Mirin RP, Nam SW. High-efficiency superconducting nanowire single-photon detectors fabricated from MoSi thin-films. OPTICS EXPRESS 2015; 23:33792-33801. [PMID: 26832040 DOI: 10.1364/oe.23.033792] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We report on MoSi SNSPDs which achieved high system detection efficiency (87.1 ± 0.5% at 1542 nm) at 0.7 K and we demonstrate that these detectors can also be operated with saturated internal efficiency at a temperature of 2.3 K in a Gifford-McMahon cryocooler. We measured a minimum system jitter of 76 ps, maximum count rate approaching 10 MHz, and polarization dependence as low as 3.3 ± 0.1%. The performance of MoSi SNSPDs at 2.3 K is similar to the performance of WSi SNSPDs at < 1 K. The higher operating temperature of MoSi SNSPDs makes these devices promising for widespread use due to the simpler and less expensive cryogenics required for their operation.
Collapse
|
8
|
Stevens MJ, Glancy S, Nam SW, Mirin RP. Third-order antibunching from an imperfect single-photon source. OPTICS EXPRESS 2014; 22:3244-60. [PMID: 24663616 DOI: 10.1364/oe.22.003244] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We measure second- and third-order temporal coherences, g((2))(τ) and g((3))(τ1,τ2), of an optically excited single-photon source: an InGaAs quantum dot in a microcavity pedestal. Increasing the optical excitation power leads to an increase in the measured count rate, and also an increase in multi-photon emission probability. We show that standard measurements of g((2)) provide limited information about this multi-photon probability, and that more information can be gained by simultaneously measuring g((3)). Experimental results are compared with a simple theoretical model to show that the observed antibunchings are consistent with an incoherent addition of two sources: 1) an ideal single-photon source that never emits multiple photons and 2) a background cavity emission having Poissonian photon number statistics. Spectrally resolved cross-correlation measurements between quantum-dot and cavity modes show that photons from these two sources are largely uncorrelated, further supporting the model. We also analyze the Hanbury Brown-Twiss interferometer implemented with two or three "click" detectors, and explore the conditions under which it can be used to accurately measure g((2))(τ) and g((3))(τ1,τ2).
Collapse
|
9
|
Zhai Y, Becerra FE, Glebov BL, Wen J, Lita AE, Calkins B, Gerrits T, Fan J, Nam SW, Migdall A. Photon-number-resolved detection of photon-subtracted thermal light. OPTICS LETTERS 2013; 38:2171-2173. [PMID: 23811867 DOI: 10.1364/ol.38.002171] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We examine the photon statistics of photon-subtracted thermal light using photon-number-resolved detection. We demonstrate experimentally that the photon number distribution transforms from a Bose-Einstein distribution to a Poisson distribution as the number of subtracted photons increases. We also show that second- and higher-order photon correlation functions can be directly determined from the photon-number-resolved detection measurements of a single optical beam.
Collapse
Affiliation(s)
- Yanhua Zhai
- Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland, 100 Bureau Drive, Gaithersburg, Maryland 20899, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Zhou Z, Frucci G, Mattioli F, Gaggero A, Leoni R, Jahanmirinejad S, Hoang TB, Fiore A. Ultrasensitive N-photon interferometric autocorrelator. PHYSICAL REVIEW LETTERS 2013; 110:133605. [PMID: 23581322 DOI: 10.1103/physrevlett.110.133605] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Indexed: 06/02/2023]
Abstract
We demonstrate a novel method to measure Nth-order (N=1,2,3,4) interferometric autocorrelation with high sensitivity and temporal resolution. It is based on the combination of linear absorption and nonlinear detection in a superconducting nanodetector, providing much higher efficiency than methods based on all-optical nonlinearities. Its temporal resolution is only limited by the quasiparticle energy relaxation time, which is directly measured to be in the 20 ps range for the NbN films used in this work. We present a general model of interferometric autocorrelation with these nonlinear detectors and discuss the comparison with other approaches and possible improvements.
Collapse
Affiliation(s)
- Zili Zhou
- COBRA Research Institute, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
| | | | | | | | | | | | | | | |
Collapse
|
11
|
Gemmell NR, McCarthy A, Liu B, Tanner MG, Dorenbos SD, Zwiller V, Patterson MS, Buller GS, Wilson BC, Hadfield RH. Singlet oxygen luminescence detection with a fiber-coupled superconducting nanowire single-photon detector. OPTICS EXPRESS 2013; 21:5005-13. [PMID: 23482033 DOI: 10.1364/oe.21.005005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Direct monitoring of singlet oxygen (¹O₂) luminescence is a particularly challenging infrared photodetection problem. ¹O₂, an excited state of the oxygen molecule, is a crucial intermediate in many biological processes. We employ a low noise superconducting nanowire single-photon detector to record ¹O₂ luminescence at 1270 nm wavelength from a model photosensitizer (Rose Bengal) in solution. Narrow band spectral filtering and chemical quenching is used to verify the ¹O₂ signal, and lifetime evolution with the addition of protein is studied. Furthermore, we demonstrate the detection of ¹O₂ luminescence through a single optical fiber, a marked advance for dose monitoring in clinical treatments such as photodynamic therapy.
Collapse
Affiliation(s)
- Nathan R Gemmell
- Scottish Universities Physics Alliance and School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK
| | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Natarajan CM, Zhang L, Coldenstrodt-Ronge H, Donati G, Dorenbos SN, Zwiller V, Walmsley IA, Hadfield RH. Quantum detector tomography of a time-multiplexed superconducting nanowire single-photon detector at telecom wavelengths. OPTICS EXPRESS 2013; 21:893-902. [PMID: 23388983 DOI: 10.1364/oe.21.000893] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Superconducting nanowire single-photon detectors (SNSPDs) are widely used in telecom wavelength optical quantum information science applications. Quantum detector tomography allows the positive-operator-valued measure (POVM) of a single-photon detector to be determined. We use an all-fiber telecom wavelength detector tomography test bed to measure detector characteristics with respect to photon flux and polarization, and hence determine the POVM. We study the SNSPD both as a binary detector and in an 8-bin, fiber based, Time-Multiplexed (TM) configuration at repetition rates up to 4 MHz. The corresponding POVMs provide an accurate picture of the photon number resolving capability of the TM-SNSPD.
Collapse
Affiliation(s)
- Chandra M Natarajan
- School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, UK.
| | | | | | | | | | | | | | | |
Collapse
|
13
|
Assmann M, Bayer M. Coherence time measurements using a single detector with variable time resolution. OPTICS LETTERS 2012; 37:2811-2813. [PMID: 22825142 DOI: 10.1364/ol.37.002811] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We present a simple technique for measuring coherence times for stationary light fields using a single detector with tunable time resolution. By measuring the equal-time second-order correlation function at varying instrument response functions it is possible to determine the coherence time and also the shape of the temporal decay without the need to record time-resolved data. The technique is demonstrated for pseudothermal light. Possible applications for dynamic light scattering and photon statistics measurements are discussed.
Collapse
Affiliation(s)
- Marc Assmann
- Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund, Germany. marc.assmann@tu‐dortmund.de
| | | |
Collapse
|
14
|
Ma L, Rakher MT, Stevens MJ, Slattery O, Srinivasan K, Tang X. Temporal correlation of photons following frequency up-conversion. OPTICS EXPRESS 2011; 19:10501-10510. [PMID: 21643305 DOI: 10.1364/oe.19.010501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We demonstrate an approach to measure temporal correlations of photons in the near infrared range using frequency up-conversion. In this approach, the near infrared signal photons are converted into the visible range, in which highly efficient silicon avalanche photodiodes are used to perform the temporal correlation measurements. A coherent light source and a pseudo-thermal light source were used in the experiment. The results are in agreement with theoretical values and those obtained from measurements directly made using superconducting nanowire single photon detectors. We conclude that the temporal correlation (up to 4th order) of photons was preserved in the frequency up-conversion process. We further theoretically and experimentally studied the influence of the dark counts on the measurement. The setup uses commercially available components and achieves high total detection efficiency (~26%).
Collapse
Affiliation(s)
- Lijun Ma
- Information Technology Laboratory, National Institute of Standards and Technology, 100 Bureau Dr, Gaithersburg, MD 20899, USA
| | | | | | | | | | | |
Collapse
|
15
|
Afek I, Ambar O, Silberberg Y. Correlated multiphoton holes: absence of multiphoton coincidence events. PHYSICAL REVIEW LETTERS 2010; 105:093603. [PMID: 20868159 DOI: 10.1103/physrevlett.105.093603] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2010] [Revised: 07/25/2010] [Indexed: 05/29/2023]
Abstract
We generate bipartite states of light which exhibit an absence of multiphoton coincidence events between two modes amid a constant background flux. These "correlated photon holes" are produced by mixing a coherent state and relatively weak spontaneous parametric down-conversion by using a balanced beam splitter. Correlated holes with arbitrarily high photon numbers may be obtained by adjusting the relative phase and amplitude of the inputs. We measure states of up to five photons and verify their nonclassicality. The scheme provides a route for observation of high-photon-number nonclassical correlations without requiring intense quantum resources.
Collapse
Affiliation(s)
- I Afek
- Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel.
| | | | | |
Collapse
|
16
|
Allevi A, Bondani M, Andreoni A. Photon-number correlations by photon-number resolving detectors. OPTICS LETTERS 2010; 35:1707-1709. [PMID: 20479857 DOI: 10.1364/ol.35.001707] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We demonstrate that by using pairs of photodetectors endowed with internal gain we are able to quantify the photon-number correlation coefficient between the two components of a pulsed bipartite state in the "mesoscopic" intensity regime (less than 100 mean photons). We compare the performances of hybrid photoemissive detectors to those of multipixel silicon photon counters and demonstrate that the absence of significant noise allows the evaluation of the variance of the distribution of the differences in photon numbers, and hence of the shot-noise level, without any correction.
Collapse
|