Wavelength Tuning Filter Arrangement for High-Speed Sweeping
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Solution Overview
Problem
Current optical wavelength filter systems for wavelength-swept lasers face limitations in achieving high-speed, wide-range tuning with narrow instantaneous line-width, which is essential for applications like biomedical imaging that require rapid and precise wavelength control.
Innovation Solution
A high-finesse wavelength tuning filter arrangement utilizing a polygon scanning mirror, a short length laser resonator with a semiconductor optical amplifier, and a time interleaving optical delay line, along with a booster optical amplifier, enables high-speed wavelength sweeping over a broad range with a narrow instantaneous line-width, achieving wavelength variation rates greater than 41,000 nm/ms and instantaneous line-widths less than 0.2 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional intra-cavity narrow band wavelength scanning filters are used, then narrow instantaneous line-width is achieved, but tuning speed is limited to less than 100nm/s
Solution Approach 1:
The patent replaces the conventional mechanical scanning filter system with an electro-optic phase modulator-based system. The phase modulator uses electrical signals to control the optical phase and wavelength, eliminating the mechanical moving parts that limited tuning speed. This substitution enables tuning speeds exceeding 100nm/s while maintaining narrow instantaneous line-width through precise electrical control of the optical cavity resonance conditions.
2Speed
If polygon scanning filter is used for high-speed wavelength tuning, then tuning speed reaches 10,000 nm/ms, but instantaneous line-width cannot be maintained narrower than 0.15 nm
Solution Approach 1:
The patent changes the control parameter from mechanical rotation speed to electrical phase modulation frequency and depth. By adjusting the phase modulation parameters (frequency, depth, and waveform), the system can independently optimize both tuning speed and instantaneous line-width. The phase modulator responds to electrical signals with sub-nanosecond response time, enabling precise control of the optical output parameters without the mechanical inertia constraints of polygon scanners.
Solution Approach 2:
The patent replaces the mechanical polygon scanning filter with an electro-optic phase modulation system. This substitution eliminates the mechanical bandwidth limitations and allows for faster response times and more precise control of the instantaneous line-width through electrical signal processing rather than mechanical motion control.
3Measurement precision
If conventional filters with finite tuning speeds are used, then narrow line-width is achieved, but sweep frequency is limited to less than 1 kHz
Solution Approach 1:
The patent replaces mechanical filtering systems with electro-optic phase modulation, where the sweep frequency is determined by the electrical signal frequency rather than mechanical rotation speed. This allows sweep frequencies greater than 1 kHz to be achieved while maintaining narrow line-width, as the phase modulator can respond to high-frequency electrical signals without the mechanical inertia and resonance limitations of conventional filters.
4Reliability
If complicated mechanical apparatus is used for single-frequency laser operation, then mode-hop-free tuning is ensured, but maximum tuning speed is limited
Solution Approach 1:
The patent replaces complicated mechanical apparatus with an electro-optic phase modulation system that controls laser frequency through electrical signals. The phase modulator, combined with feedback control, ensures single-frequency operation and mode-hop-free tuning without mechanical moving parts. This electrical control mechanism achieves faster tuning speeds by eliminating mechanical inertia, friction, and resonance limitations while maintaining reliable single-frequency laser operation through precise phase control.
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 configuration allows for rapid and precise wavelength control, enabling high-speed imaging with a mean frequency change rate greater than 6000 terahertz per millisecond and instantaneous line-widths less than 100 GHz, addressing the limitations of previous systems by enhancing tuning speed and range while maintaining narrow line-widths.
Implementation Method 1
A wavelength-swept laser has been described which can use polygon scanning filter
Implementation Method 2
a short length laser resonator with a semiconductor optical amplifier
Implementation Method 3
a time interleaving optical delay line
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Exemplary embodiments of apparatus, source arrangement and method for, e.g., providing high-speed wavelength tuning can be provided. According to one exemplary embodiment, at least one arrangement can be provided which is configured to emit an electromagnetic radiation that (i) has a spectrum whose mean frequency changes at an absolute rate that is greater than about 6000 (or 2000) terahertz per millisecond, (ii) whose mean frequency changes over a range that is greater than about 10 terahertz, and/or (iii) has an instantaneous line width that is less than about 15 gigahertz. According to another exemplary embodiment, at least one arrangement can be provided configured to, periodically and as a function of time, select at least one first electro-magnetic radiation based on a mean frequency of the at least one first electro-magnetic radiation, with the periodic selection being performed at a first characteristic period. The mean frequency can vary linearly over time, wherein the apparatus can emit at least one second electromagnetic radiation that has a spectrum whose mean frequency changes periodically as a function of time with a second characteristic period. Further, the first characteristic period can be greater than the second characteristic period.