Pulsed Coherent White Light Source for Reflectivity Measurement
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Solution Overview
Problem
Conventional methods for measuring the reflectivity of optical surfaces are limited by the stability of light sources, making it difficult to measure highly reflective mirrors with losses below 1,000 ppm, and require multiple light sources for different wavelengths, increasing maintenance and alignment efforts.
Innovation Solution
A pulsed coherent white light source with a broad spectral bandwidth, potentially generated by a supercontinuum laser and photonic crystal fiber, is used to measure reflectivity and transmittivity across various wavelengths without the need for multiple light sources, allowing for cavity ring-down spectroscopy and reflectometry with enhanced flexibility and reduced maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional light sources are used for measuring reflectivity, then the measurement setup is simple, but the measurement precision is insufficient for highly reflective mirrors with losses below 1,000 ppm
Solution Approach 1:
The patent employs pulsed laser excitation instead of continuous wave illumination. The periodic pulsed action allows time-resolved detection of the cavity ring-down signal, enabling precise measurement of reflectivity by detecting the decay rate of light intensity over time rather than relying on steady-state intensity comparisons that are limited by light source stability.
Solution Approach 2:
The measurement system uses feedback through comparing the decay rates of light intensity in the optical cavity with and without the optical element under test. This feedback mechanism allows the system to determine reflectivity by measuring the difference in energy loss rates, compensating for light source instability through differential measurement.
2Adaptability or versatility
If multiple laser diodes are used to cover different wavelength ranges, then the adaptability for measuring different wavelengths is improved, but the device complexity and maintenance effort increase
Solution Approach 1:
The patent uses a single broadband supercontinuum laser source that can operate across multiple wavelength ranges (visible and infrared) instead of requiring separate laser diodes for each wavelength range. This universal light source performs multiple functions by adjusting its emission wavelength, eliminating the need for multiple specialized light sources and reducing system complexity.
Solution Approach 2:
The system achieves wavelength tunability by changing the operational parameters of the supercontinuum laser source, specifically adjusting the pump laser wavelength and the dispersion characteristics of the photonic crystal fiber. This allows a single light source to cover multiple wavelength ranges by modifying its physical parameters rather than using multiple fixed-wavelength sources.
3Ease of operation
If diode lasers are used for cavity ring-down reflectometry, then the setup is simple, but the flexibility for characterizing optical surfaces at different wavelengths is limited
Solution Approach 1:
The patent maintains operational simplicity while achieving wavelength flexibility by using a supercontinuum laser source whose emission spectrum can be tuned by changing the pump laser wavelength and fiber dispersion parameters. The basic cavity ring-down measurement procedure remains simple, but the wavelength parameter is made variable, combining ease of operation with spectral flexibility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables precise measurement of reflectivity and transmittivity at various wavelengths, including those inaccessible with traditional laser diodes, reducing maintenance and alignment efforts while providing sensitive characterization of highly reflective and transmissive optical surfaces.
Implementation Method 1
A pulsed coherent white light source, potentially generated by a supercontinuum laser and photonic crystal fiber
Implementation Method 2
A pulsed coherent white light source, potentially generated by a supercontinuum laser and photonic crystal fiber
Implementation Method 3
For cavity ring-down measurements an optical cavity is employed, wherein the optical surface, whose reflectivity and/or transmittivity is to be measured, is integrated in the optical cavity
Implementation Method 4
A laser pulse is coupled into the optical cavity and the light or optical power leaking out of the cavity is measured. Based on the decay of the light or optical power leaking out of the cavity, the cavity losses can be derived
Implementation Method 5
Conventional methods for measuring the reflectivity of optical surfaces
Implementation Method 6
measuring the reflectivity and/or transmittivity of an optical surface
Data Source
AI summary
An apparatus and a method measure a reflectivity and/or transmittivity of an optical surface. The apparatus includes a pulsed coherent white light source for generating pulsed coherent white light, wherein the apparatus is adapted to irradiate the optical surface with at least a part of the generated pulsed coherent white light.