Cold Mirror Research Articles

Design and Performance of the Upgraded Mid-infrared Spectrometer and Imager (MIRSI) on the NASA Infrared Telescope Facility

We describe the new design and current performance of the Mid-InfraRed Spectrometer and Imager (MIRSI) on the NASA Infrared Telescope Facility (IRTF). The system has been converted from a liquid nitrogen/liquid helium cryogen system to one that uses a closed-cycle cooler, which allows it to be kept on the telescope at operating temperature and available for observing on short notice, requiring less effort by the telescope operators and day crew to maintain operating temperature. Several other enhancements have been completed, including new detector readout electronics, an IRTF-style standard instrument user interface, new stepper motor driver electronics, and an optical camera that views the same field as the mid-IR instrument using a cold dichroic mirror, allowing for guiding and/or simultaneous optical imaging. The instrument performance is presented, both with an engineering-grade array used from 2021 to 2023, and a science-grade array installed in the fall of 2023. Some sample astronomical results are also shown. The upgraded MIRSI is a facility instrument at the IRTF available to all users.

Investigating focal macular electroretinogram function for fundus‐related perimetry application

Aims/Purpose: This study aimed to investigate the utility of focal macular electroretinogram (ERG) function in fundus‐related perimetry (microperimetry) for assessing cryptogenic diseases such as macular dystrophy. The decline in visual sensitivity of the retina was measured using microperimetry, and the retinal layer causing this decline was identified using multifocal ERG.A focal macular ERG function was used for microperimetry instead of multifocal ERG.Methods: The developed apparatus comprised illumination and photographic optical systems separated by a mirror with a hole, a microperimetry optical system and an ERG optical system separated by a 45° cold mirror. It also consisted of an Edmund infrared camera EO‐50231, a lens, a halogen lamp, an objective lens, four double convex lenses, two aperture stops, a mirror, a 12.1‐inch high brightness (2000 cd/m2) monitor and an artificial eye. Its electrical measuring equipment included a differential amplifier, a high‐pass filter, a 50‐Hz notch filter and two non‐inverting amplifiers. Moreover, the equipment consisted of the National Instruments' I/O device USB‐6216, a shielded connector block, plate electrodes, an electromagnetic shield sheet and the LabVIEW 2018 software for data retrieval. To perform the focal macular ERG, a DynaScan 49‐inch ultrahigh brightness (3500 cd/m2) liquid crystal display (LCD) was prepared.Results: The ERG software could display three stimulus spot circles with diameters of 5°, 10° and 15° on the ultrahigh brightness LCD. Additionally, a function for adjusting the size of the stimulus spot circle was added as the diameter was changed from 1° to 15°. The focal macular ERG was able to measure a wave, b wave and photopic negative response (PhNR). It was found that certain small waves on the b wave were confirmed with high probability as oscillatory potentials (OPs), while one positive wave similar to the d wave was confirmed sometimes; however, the c wave was not confirmed.Conclusions: It can be concluded that when not only the a wave, b wave and PhNR but also the OPs and d wave are confirmed, the focal macular ERG function can identify the retinal layer causing visual alterations at specific points throughout the retina.

Conceptual layout of a helium cooling system for the Einstein Telescope

The Einstein Telescope (ET) is a 3rd generation gravitational-wave detector planned in triangular shape with 10 km arm lengths in an underground installation at a depth of 200m to 300 m. While 2nd generation detectors and the ET high-frequency interferometer are operated at room-temperature, the ET low-frequency (LF) interferometer shall be operated at cryogenic mirror temperatures of 10K to 20K in order to reduce the thermal noise. Considering thermal dissipation limits in the heat extraction path from the mirror to the heat sink, He-II provides ultra-low-noise cooling to allow for an interferometer sensitivity at levels below 1 × 10−20 m/ in the detection band. In order to limit particle adsorption on the cold mirror surface, the total pressure in the cryostat must be reduced to p ≤ 1 × 10−10 mbar, i.e. partial pressures of water and heavier components pi ≤ 1 × 10−14 mbar, respectively, using a cryopump/shield around the mirror that is cooled with supercritical helium to T ≈ 5K.We present the conceptual layout of a helium cooling system that can provide cooling power for several ET-LF cryostats and their corresponding cryotraps, including mirror cooling at 2K as well as thermal shielding at 5K and at 50K to 80K. A process flow diagram focuses on the cooling system’s key components with their locations and their interconnections. On the diagram’s basis, we explain the cooldown process and steady-state operation, ranging from outer shield and cryotrap cooling to the formation of He-II in the mirror heat extraction path.

Solar spectral beam splitting for photochemical conversion and polygeneration

Conversion efficiency from sunlight to electricity is relatively low for both solar thermal and photovoltaic converters, where more than three quarters of the solar energy is dissipated back to the environment. Division of the solar spectrum (spectral splitting) enables better use of photon energy in each spectral band. Here we present a polygeneration approach to solar energy conversion where the main contribution is a photochemical process, while co-producing power and medium grade heat. A collector design is introduced with a linear Fresnel lens, a ‘cold mirror’ spectral filter, and photochemical, photovoltaic, and thermal converters. To illustrate a wide scope of applications, three photochemical options are investigated: photonitrozation of cyclohexane, photooxigenation of citronellol, and catalytic disinfection of wastewater. The analysis of conversion efficiency uses detailed optical modeling based on realistic (commercially available) component properties and on experimental characterization of participating compounds. Overall system efficiency is up to 50%. The amount of electricity displaced or saved vs. current lamp-driven photochemical processes can reach as high as 97% of the incident solar energy, for several combinations of photochemical and photovoltaic converters. The polygeneration approach can be implemented using low-cost components and may lead to cost-effective, highly efficient solutions with a significant contribution to displacement of conventional energy sources.

Slit-based photoacoustic tomography with co-planar light illumination and acoustic detection for high-resolution vascular imaging in human using a linear transducer array.

Slit-based photoacoustic tomography is a high-resolution three-dimensional imaging technique for linear transducer array. The system was based on acoustic diffraction through a thin slit to increase the elevation coverage and spatial resolution. In this study, we introduce the third-generation slit-based photoacoustic tomography system with co-planar light illumination and acoustic detection. The new system possesses several innovations. First, we utilized an optically transparent slit, which enables both light illumination and acoustic diffraction. Second, we used a combination of cold and hot mirrors to provide co-planar light illumination and acoustic detection. Third, we designed a waterproof transducer array with a long acoustic focus tailored for the co-planar setup. Compared to the previous generations, which used side-illumination and metal slit, the new system provides a larger field of view and deeper imaging depth in a more compact manner. We tested the system in both phantoms and in vivo imaging. Detailed vascular structures from different regions can be clearly revealed, making the system valuable for translational imaging applications.

Development of superimposing electroretinogram for identifying the retinal layer causing a decline in visual sensitivity at arbitrary points on the retina

AbstractPurposeAlthough the decline in visual sensitivity of the retina can be measured by microperimetry, it is difficult to identify the retinal layer causing this decline. We investigated cryptogenic diseases, such as macular dystrophy, by developing an electroretinogram (ERG) superimposing seven multifocal hexagonal stimulus arrays on the background of a multifocal array.MethodsThis apparatus is made of illumination and photographic optical systems separated by a mirror with a hole. In addition, it is made of a microperimetry optical system and an ERG optical system separated by a cold mirror. The device consists of an Edmund infrared camera EO‐50231, a lens with a 25‐mm focal length, a halogen lamp, an objective lens with a 50‐mm focal length, 4 double convex lenses with a 100‐mm focal length, 2 aperture stops, a mirror, a 45° cold mirror, an 8‐inch monitor and an artificial eye. We deployed a differential amplifier with gain 10, high‐pass filter with a 21.2‐Hz cut‐off frequency, 60‐Hz notch filter and two non‐inverting amplifiers with gains 1001 and 11. Moreover, we used the National Instruments' I/O device USB‐6212, the Nihon Kohden's plate electrode NE‐113A, the Nihon Kohden's electromagnetic shield sheet Y049 and the LabVIEW 2018 software for data retrieval. The background of the ERG software consists of 11 layers and 330 arrays and uses seven arrays as the examination target. The centre of these seven arrays has the same area, with an array directly placed under it on the background; and the system superimposes these arrays. We developed the ERG software, which was able to display the adjusted background from 18.0 to 30.0 mm and it almost did not have the delay time of a flicker stimulation as the frequency was changed from 10 to 100 Hz. The ERG software was shown on an HP Pavilion 32‐inch HDR display.ResultsAt the arbitrary position on the fundus, the superimposing ERG was able to measure all waveforms: a wave, b wave, c wave, and photopic negative response. Cone ERG and bright flash ERG were good.ConclusionsIt is expected that the superimposing ERG function would identify the retinal layer causing visual alterations at specific points throughout the retina. Further work towards pre‐clinical animal testing and clinical evaluation are required.

Performance Comparison Between Hot Mirror and Cold Mirror as a Beam Splitter on Photovoltaic - Thermoelectric Generator Hybrid Using LabVIEW Simulator

Solar energy can be converted into electrical energy using photovoltaic (PV) and thermoelectric generators (TEG). In order to increase the effectiveness of energy absorption, a hot mirror or cold mirror spectrum separator is used. In this study, a simulation was carried out to see the effect of the cold mirror and hot mirror spectrum separator on the performance of the PV-TEG hybrid. Simulations are carried out using the LabVIEW program. The standard for the solar radiation spectrum used is AM1.5D. The incoming radiation is transmitted using a Fresnel lens to make it more focused and then transmitted to a cold mirror or hot mirror, where the spectral irradiance will be halved. Spectral irradiance with a wavelength of 400-690 nm will be directed to PV and a wavelength of 710-1150 nm will be directed to TEG. From the PV-TEG hybrid modeling and simulation using the LabVIEW program, the resulting power and efficiency are 240.635 W/m2 and 27% respectively for cold mirror and 228.835 W/m2 and 25.76% for hot mirror.

Cryogenic vacuum considerations for future gravitational wave detectors

In recent years, gravitational wave observatories have conquered the world science scene due to their unprecedented capability to observe astrophysical signals. Those first observations opened up multimessenger astronomy and called for a tremendous R effort to improve the sensitivity of future detectors. One of the many issues to be solved, not to affect the desired sensitivity, is the noise induced by the use of room temperature mirrors, especially for the low-frequency detection range. The use of cryogenic mirrors to reduce such a noise source has been individuated as a viable solution to obtain the desired sensitivity at low frequency. Cryogenically cooled mirrors, routinely operating at 10 K, present a number of extraordinary challenges, one being the cryogenic vacuum system hosting the cold mirrors. Gases composing the residual vacuum will tend to cryosorb and build a contaminant ice layer (``frost'') on the mirror surface. Depending on such ice layer thickness, various unwanted detrimental effects may occur affecting mirror performances. This paper analyzes the consequences of hosting a cryogenically cooled mirror in a vacuum system and sets new limits for an acceptable operating pressure to avoid frost formation in a given period of continuous data taking. Since ice formation can be reduced but not avoided, we analyze potential mitigation methods to cure such a phenomenon. Thermal and nonthermal methods are analyzed and compared. Electron stimulated desorption is also considered as an alternative method to desorb the ice layer on mirrors. Finally, we briefly discuss further studies needed to validate the various methods with special care on their effects on the mirror perfection and optical properties.

Soiling Comparison of Mirror Film and Glass Concentrating Solar Power Reflectors in Southwest Louisiana

Soiling effects influence the output of solar thermal plants, significantly causing unwanted transmittance, reflectance, and absorbance losses. Research is needed to identify what type of reflective surfaces are best suited for semitropical climates, such as the southeastern United States. This paper initially presents a review of several concentrating solar power (CSP) reflector testbeds used to analyze the soiling effects of various reflective materials. A soiling testbed is developed for this study that comprised six sets of reflective surfaces mounted at a fixed tilt of 30 degrees: three sets of thin-film surfaces and three sets of glass types. Two generations of 3M solar mirror film (SMF), 3M SMF 1100 and 3M SMF 2020, were used along with Konica Minolta SMF, silvered Corning Willow Glass, a dichroic cold mirror, and a standard mirror. Results show that the 3M SMF 2020 and Konica Minolta SMF performed the best during regular cleaning intervals, whereas the silvered Corning Willow Glass gave the best performance if only cleaned naturally. The other glass types showed the least average loss due to soiling throughout this study but gave the lowest performance for specular reflection.

Design High performance multilayers cold mirror

The optical design process includes a myriad of tasks that the designer must be performed and consider in the process of optimizing the performance of the optical system. In this article, a design based on four groups of materials for a multilayer dielectric cold mirror: V2O5 \\MgF2, Sic\\MgF2, TiO2\\MgF2, and Al As\\MgF2 where MgF2 represents low refractive index and other material in each group represent high refractive index. A cold mirrors are a special dielectric mirrors that reflects the entire visible wavelength band, while the transmitting infrared wavelength band. These systems of mirrors are constructed for an event angle from 0° to 45° and are modeled with interference filters-like multi thin layer dielectric coatings. The results of our work designed shows the mirror based on Al As/MgF2 is the most promising design for cold mirror with the highest reflection in the visible region and the highest Transition in the IR region. In the spectrum range of 400-800 nanometers, the average transmission is much less than 1 %, while the average transmission is 95 percent in the wave band 800-2500 nanometer.

Effect of Nasal Dominance on Pulmonary Function Test and Heart Rate: A Pilot Study.

Background: The nasal cycle is one of the many cyclic events in a human being. Nasal airflow is greater in one nostril at any given point in time and this alternates between right and left nostrils over time. Its periodicity ranges from 25 min to 8 h. This alteration has been known to be controlled by the autonomic nervous system. The current study was designed to assess the effect of nasal dominance during rest on pulmonary function parameters and heart rate.Materials and Methods: A cross-sectional study was done on 35 apparently healthy individuals of the age group of 18–30 years. Based on a cold mirror test, the participants were categorized into two groups of right nasal dominance (RND) and left nasal dominance (LND). The parameters recorded were forced expiratory volume in the first sec (FEV1), forced vital capacity (FVC), FEV1/FVC, peak expiratory flow rate, forced expiratory flow between 25%-75%, SpO2, and pulse rate. Data were expressed as mean ± standard deviation and were analyzed using SPSS version 20.Results: All pulmonary function parameters exhibited higher values in RND participants compared to LND participants and the difference was found to be statistically significant (P < 0.05).Conclusion: Nasal dominance has a measurable effect on pulmonary functions and heart rate hence emphasizing the role of autonomic control of airways. This influence can be used as adjuvant therapy for certain disorders.

Tunable dual-band terahertz absorber with all-dielectric configuration based on graphene.

In this paper, we theoretically design a dual-band graphene-based terahertz (THz) absorber combining the magnetic resonance with a THz cold mirror without any metallic loss. The absorption spectrum of the all-dielectric THz absorber can be actively manipulated after fabrication due to the tunable conductivity of graphene. After delicate optimization, two ultra-narrow absorption peaks are achieved with respective full width at half maximum (FWHM) of 0.0272 THz and 0.0424 THz. Also, we investigate the effect of geometric parameters on the absorption performance. Coupled mode theory (CMT) is conducted on the dual-band spectrum as an analytic method to confirm the validity of numerical results. Furthermore, physical mechanism is deeply revealed with magnetic and electric field distributions, which demonstrate a totally different principle with traditional plasmonic absorber. Our research provides a significant design guide for developing tunable multi-resonant THz devices based on all-dielectric configuration.

Low Sun Spectrum on Simulation of a Thin Film Photovoltaic, Heat Absorber, and Thermoelectric Generator System

The research presents the simulation results with Matlab on combining of a type of thin-film photovoltaic module (a-Si), a copper plate heat absorber with thermoelectric generators (TEG) utilizing the standard low-sun spectrum AM1.5G at 0.05, 0.06, 0.07, 0.08, 0.09 and 0.1 Sun as a source of radiation. Amorphous silicon is a type of thin-film solar cell that is more suitable for indoor use so that by using a source of low-intensity light radiation from the sun will still generate electrical energy conversion. Spectrum splitting is used as a cold mirror, which reflects the spectrum of light to the a-Si module in the form of photon energy while transmitting to the TEG module the spectrum of near-infrared light radiation in the form of heat. On the hot side of the TEG, a copper plate was placed to accommodate the heat from light radiation to increase convection heat transfer and temperature ifferences between the hot and cold sides of the TEG. The simulation results show that the highest efficiency of a-Si module is 3.46% achieved at the lowest spectrum of 0.05 Sun, vice versa TEG is at the highest spectrum at 0.1 Sun and 10.05% its efficiency. This low sun spectrum will be a milestone in the utilization of bulb radiation energy in general domestic needs.

Thin SiNC/SiOC Coatings with a Gradient of Refractive Index Deposited from Organosilicon Precursor

In this work, optical coatings with a gradient of the refractive index are described. Its aim was to deposit, using the RF PECVD method, films of variable composition (ranging from silicon carbon-oxide to silicon carbon-nitride) for a smooth change of their optical properties enabling a production of the filter with a refractive index gradient. For that purpose, two organosilicon compounds, namely tetramethyldisilazane and hexamethyldisilazane, were selected as precursor compounds. The results reveal better optical properties of the materials obtained from the latter source. Depending on whether deposited in pure oxygen atmosphere or under conditions of pure nitrogen, the refractive index of the coatings amounted to 1.65 and to 2.22, respectively. By using a variable composition N2/O2 gas mixture, coatings of intermediate magnitudes of “n” were acquired. The optical properties were investigated using both UV-Vis absorption spectroscopy and variable angle spectroscopic ellipsometry. The chemical structure of the coatings was studied with the help of Fourier transform infrared and X-ray photoelectron spectroscopies. Finally, atomic force microscopy was applied to examine their surface topography. As the last step, a “cold mirror” type interference filter with a gradient of refractive index was designed and manufactured.

APPLICATIONS OF CHEMICALLY SYNTHESIZED CUS: PBO ALLOYED THIN FILMS IN MULTILAYER SOLAR CELLS AND OPTOELECTRONICS

CuS: PbO, alloyed thin films were successfully deposited on glass substrates under the deposition condition of 40oC of NaOH solution, using two solution based methods: successive ionic layer adsorption and reaction (SILAR) and solution growth technique. The crystallographic studies were done using X-ray diffractometer (XRD) and scanning electron microscope (SEM). The deposited alloyed samples were annealed at 250oC and 1500C. using Master Chef Annealing Machine. Rutherford backscattering Spectroscopy (RBS) analysis confirmed the percentage of the elements of copper, lead, sulphur and oxygen in the alloyed thin films. The optical characterization was carried out using UV-1800 double beam spectrophotometer. Sample cp1 annealed at 250 oC has an optical transmittance of 27% -71% in the ultraviolet region, 71%-83% in the visible and 83%-88% in the near infrared regions of electromagnetic spectrum. The alloyed thin films of samples cp2 of CuS:PbO annealed at 150oC, show optical transmittance of 15%-61% in the ultraviolet region, 61%-59% in the visible, and becomes linear through the near-infrared regions of electromagnetic spectrum. The two samples, have equal direct wide band gap of 3.65±0.05eV. From the spectral qualities, these compounds alloyed thin films may found useful in passive layer in heat and cold mirror application, vulcanization in tyre production due its thermal stability, active multilayer in various types of solar cells, liquid crystal displays, flat panel displays for optoelectronic applications and gas censor applications.

A New Simulation of Photovoltaic and Thermoelectric Generator Hybrid System with a Beam Splitter Cold and Hot Mirror for Low Intensity

In this study, the simulation of Photovoltaic (PV) and Thermoelectric Generator (TEG) hybrid was developed using a spectrum splitter. The simulation was carried out by using the AM1.5G solar spectrum as a standard for 1 Sun, with a variation of 0.05, 0.1, 0.25, 0.50, and 0.7 Suns. The light spectrum was concentrated by using a Fresnel lens and then transmitted to a spectrum splitter. Spectrum splitter that was used is a hot and cold mirror with dimensions of 50 × 50 mm, which is positioned at the angle of 45o from the Fresnel lens’s direction. Additionally, PV used is a type amorphous Silicon (a-Si) and TEG types of Bismuth telluride (Bi2Te3). The simulation result shows that by using a cold mirror, its maximum total power is better than a hot mirror. In addition, the Suns and temperature changes have a significant effect on the output power and efficiency of the hybrid. Particularly at 0.7 suns, 25 °C PV temperature, and 55 °C hot-side temperature of TEG, the power obtained was 0.096 W/m2, and the efficiency was 50.37% compared to the hot mirror, which is relatively lower, accounted for 0.094 W/m2 and 48.07%.

Design of Microscope Optics for the Acquisition of Multiple Wavelength Band Image.

We design combinations of filters that lead to make outputs of multiple wavelength bands simultaneously. These bands are either 1) Infrared, RGB, Ultraviolet-3ranges 2) IR, Red, Green, Blue, UV-5ranges 3) IR+ Red, Green, Blue+UV-3ranges. Each is mostly devised by the arrangement of normal cold mirror, UV cold mirror, Philips(RGB) prism, UV filter and color filter. For the selection 1), UV cold mirror reflects UV and transmit VIS + IR. VIS and IR are sorted by normal cold mirror, which passes IR and reflects VIS. Each sorted light goes to each sensor to capture the images. The sorting of VIS and UV also can be done by UV filter. For the selection 2), have a same process in 1) but make VIS pass Philips(RGB) prism which sorts VIS into R, G, B. For the selection 3), the light passes green color filter first, Green color is only transmitted and the others are reflected. And then reflected light goes through UV cold mirror so that UV and Blue (wavelength <; 500nm) are reflected. And the others(wavelength>550nm, but green color zone was already sorted roughly wavelength>600nm) are transmitted, which is Red and IR. This sorting can be done by another design. After sorting all ranges by the selection 2), we can arrange UV goes a same pass with blue, and IR with red. We need band pass filters (in here, color filters) to revise the passes.

Potential energy of photon passes through cold mirror on photovoltaic-thermoelectric generator with artificial lights radiation

The amount of photon energy becomes a key parameter that determines the release of electron bonds which is often called a band-gap in photovoltaic cells (PV) to generate electricity. This paper presents the results of measurements of photon energy from radiation sources of artificial light Halogen, Incandescent and Xenon which aims to adjust the bad gap type of solar cell material. Simulations of measuring 50 watts of bulb radiation were carried out repeatedly with the Spectrometer sensor and the application software Spectragryph 1.2.8 on each electron Volt the bulb light. The incoming radiation form the bulb is concentrated with a Polymethylmetacrylate (PMMA) Fresnel lens with an optimal light transmission capability of 92%. The results of this light transmission will be divided after illuminating at the Cold mirror (CM) spectrum splitterr, partly reflected in the PV module and partially transmitted to the thermoelectric generator (TEG) in the PV-TEG hybrid. The measurement of photons leading to PV show values of 2.2 and 2.4 eV for Halogen with Cadmium Sulfide that match the band-gap for the photon’s energy. While the Incandescent photon energy, it is more suitable with PV material in Silicon, Germanium and Indium nitride. For Xenon, it gives the effect of releasing electrons bond to Cadmium sulfide and band gap which is below 2.42 eV, such as CdSe, InN and Si. The maximum light intensity reflected by CM is emitted by a Xenon bulb, then Halogen and the lowest is Incandescent (50> 40> 36) a.u., respectively. Meanwhile, the energy of the photons transmitted to the TEG module illustrates a different trend, where the best Halogen is followed by the lowest then Xenon incandescent.

Regional alterations in human choroidal thickness in response to short-term monocular hemifield myopic defocus.

To examine the regional changes in human choroidal thickness following short-term exposure to hemifield myopic defocus using optical coherence tomography (OCT). The central 26˚ visual field of the left eye of 25 healthy young adults (mean age 26±5years) was exposed to 60min of clear vision (control session), +3 D full-field, +3 D superior retinal and +3 D inferior retinal myopic defocus, with the right eye occluded. Choroidal thickness across the central 5mm (17°) macular region was examined before and after 60min of defocus using a high-resolution, foveal centred vertical OCT line scan, with optical defocus simultaneously imposed using a Badal optometer and cold mirror system mounted on a Spectralis OCT device. Averaged across the central 5mm macular area, choroidal thickness decreased by -4±7μm during the control session (p=0.01), most likely due to the unique stimulus conditions of this study. The mean macular choroidal thickness increased during full-field (+2±8μm), inferior retinal (+3±7μm) and superior retinal myopic defocus (+5±9μm), representing a significant thickening of the choroid compared to the control session (all p<0.05). The defocus induced changes in macular choroidal thickness differed between the superior and inferior hemiretinal regions (F2.26, 54.27 =29.75, p<0.001). When only the superior retina was exposed to myopic defocus, the choroid thickened in the superior region (+7±8μm, p<0.001), but did not change significantly in the inferior region (+3±9μm, p=0.12). When only the inferior retina was exposed to myopic defocus, the choroid thickened inferiorly (+4±8μm, p=0.005), with no significant change observed in the superior region (+1±8μm, p=0.46). These findings provide evidence supporting a local regional choroidal response to myopic defocus in the human eye, with hemifield myopic defocus leading to significant thickening of the choroid localised to the retinal region exposed to defocus. The novel finding of a localised response of the human choroid to hemifield myopic defocus, particularly in the superior hemiretina, may have important implications in optimising the optical design of myopia control interventions.

Molecular adsorbed layer formation on cooled mirrors and its impacts on cryogenic gravitational wave telescopes

Cryogenic mirrors have been introduced to the KAGRA gravitational wave telescope in Japan, and are also planned to be used in next-generation gravitational wave telescopes to further improve their sensitivity. Molecular gases inside vacuum chambers adhere to cold mirror surfaces because they lose their kinetic energy when they hit cryogenic surfaces. Finally, a number of adsorbed molecules form an adlayer, which will grow with time. The growing adlayer functions as an optical coating and changes the properties of the underlying mirror, such as reflectance, transmittance, and absorption, which are carefully chosen to maximize the detector sensitivity. The adlayer possibly affects the gravitational wave detector sensitivity. In order to characterize these changes, a high-finesse Fabry--Perot cavity was introduced to a KAGRA cryostat and the finesse of the cavity was monitored for 35 days under cryogenic conditions. We confirmed that the molecular adlayer was formed on a cold mirror and caused an oscillation in the finesse. The real and imaginary parts of the refractive index of the adlayer were $1.26 \pm 0.073$ and $2.2 \times 10^{-7} \pm 1.3 \times 10^{-7} $, respectively. These are considered to be that of $\mathrm{H_2O}$ molecules. The formation rate of the molecular adlayer was 27 $\pm$ 1.9 $\mathrm{nm/day}$. In this paper, we describe theoretical and experimental studies of the formation of a molecular adlayer on cryogenic mirrors. Furthermore, the effects of a molecular adlayer on the quantum noise and the input heat to the test mass are also discussed.