Laboratory of Spectral Optical Interferometry
The laboratory performs non-contact and non-destructive optical measurements using the methods of optical coherence tomography and spectral optical interferometry. It offers 3D imaging and analysis of multilayer samples, determination of thicknesses and optical parameters, measurement of optical radiation power, and fusion splicing of optical fibres.
Description of Activities
Description of the Service
Tomographic (volumetric) imaging of multilayer samples with a layer thickness above 100 microns, determination of layer thicknesses and preparation of cross-sectional images in different planes of the sample
Detailed description of the service: Using the optical coherence tomography instrument OMES Optores Megahertz OCT System, operating in the near-infrared region (central wavelength of 1300 nanometres), tomographic (3D) images of biological samples and samples with a multilayer structure are produced in a non-contact and non-destructive manner. Using image-processing software, a map of the thicknesses of the individual layers can be constructed and images can be produced in different planes of the sample (x-y; x-z; y-z). The field of view in x-y is a maximum of 10 by 10 millimetres. The penetration depth can reach 5 millimetres, depending on the absorption and scattering of light by the sample. The method also makes it possible to monitor dynamic changes occurring inside the sample through statistical processing of changes in the speckle signal. Suitable samples for examination are those that transmit light, do not absorb it and scatter it only weakly in the near-infrared range from 1260 to 1360 nanometres, and that have a thickness of not less than 100 micrometres.
Measurement of the spectrum of radiation reflected from samples and calculation of optical parameters and thickness from the measured spectra
Detailed description of the service: Using an Ocean Insight – FLAME-S-VIS-NIR spectrometer (range from 190 to 1100 nanometres), an R200-7-VIS-NIR reflection probe and an Ocean Insight – HL-2000-LL white light source, the spectra of radiation reflected from various thin-film structures can be measured. Spectra can be recorded with different integration times (1 ms – 65s), and the power of the white light source can be adjusted up to 7 W. Using purpose-developed software, the layer thickness and various optical parameters, such as refractive and absorption indices, absorption coefficient, optical band gap, Urbach energy, etc., are calculated from the measured spectra. Suitable samples are those whose layers do not exceed 1-2 micrometres.
Measurement of optical radiation power
Detailed description of the service: Measurement of optical radiation power with an Ophir instrument, Model: StarLite, and a PD300-IR sensor. The radiation must be in the spectral range from 700 to 1800 nanometres, with a radiation power of up to 300 mW. Changes in the radiation of the order of 0.01 nW can be monitored and recorded over an extended period of time.
Fusion splicing of optical fibres
Detailed description of the service: Using an optical fibre fusion splicer – Fujikura FSM-31S – and the fibre preparation tools, various optical fibres can be spliced – single-mode and multimode, with a cladding diameter of 125μm. Splices have a loss of 0.02 dB to 0.08 dB, depending on the type of optical fibre.
Equipment
Optical coherence tomography system – Optores, Model – OMES Optores Megahertz OCT System
- Capability to acquire 2D and 3D images and live 3D visualisation
- Central wavelength 1309 nm
- FWHM (spectral emission width) – 100 nm
- Lateral (in the x-y plane) resolution (air) 30 μm and 40 μm
- Axial (depth) resolution (air) 17 μm
- Field of view 10 mm x 10 mm
- Penetration depth up to 5 mm, depending on the sample
- Specialised software for recording and processing 2D and 3D data.
Spectrometer Ocean Insight – FLAME-S-VIS-NIR; reflection measurement probe R200-7-VIS-NIR and white light source Ocean Insight – HL-2000-LL
- Detector spectral range – 190 – 1100 nm;
- Slit size 25 μm x 1 mm;
- Variable integration time in the range 1 ms – 65s.
- Reflection measurement probe with a wavelength range of 400 – 2100 nm
- Software for recording and processing spectroscopic data
- White light source with an emission range of 360 – 2400 nm and an output light power of up to 7 W
Optical radiation power meter – Ophir, Model: StarLite + PD300-IR sensor
- Photodiode optical radiation sensor with a measurement range of λ = 700 – 1800 nm and a measurable power of up to 300 mW;
- Power resolution 0.01 nW.
Optical fibre splicer – Fujikura FSM-31S
- Capable of splicing the following types of optical fibre: SMF (G.652/657), MMF (G.651), DSF (G.653), NZDSF (G.655).
- Coating (cladding) diameter of the fibres to be spliced: 125μm.
- Cleave length in the range 5-13 mm.
- Typical splice loss of 0.05 dB (SM), 0.02 dB (MM), 0.08 dB (DS) and 0.08 dB (NZDS).
- Splicing (fusion) time of 6 to 9 seconds.
- Observation and magnification method: dual-axis CMOS camera with a colour LCD display.
- Electrode life – up to 5000 splices.
Access to the Laboratory of Spectral Optical Interferometry
The Laboratory of Spectral Optical Interferometry is part of the research infrastructure of the National Centre of Excellence “Mechatronics and Clean Technologies” and is located on the Geo Milev campus. Requests for access and for joint research are therefore handled centrally — see Contacts. In addition, a full overview of the Centre’s other laboratories is available on the page Infrastructure and Laboratories.
The spectral optical interferometry equipment was established under project BG16RFPR002-1.014-0006, funded under the Programme “Research, Innovation and Digitalisation for Smart Transformation” 2021–2027, co-funded by the European Union through the European Regional Development Fund.