Tunable Laser Diode Heater Pre-emphasis Control
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Solution Overview
Problem
Wavelength tunable semiconductor laser diodes (t-LDs) with heaters struggle to quickly and stably re-tune emission wavelengths due to the slow thermal response of semiconductor materials, leading to longer re-tuning times exceeding one millisecond.
Innovation Solution
A laser apparatus and method that utilize a controller to supply pre-emphasis power to heaters before and after re-tuning, adjusting the power from a first power Pa to a second power Pb, with the pre-emphasis power Pp set greater than Pb when Pb is greater than Pa, and less than Pb when Pb is less than Pa, to enhance the thermal response and shorten the time to stabilize the emission wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If thermal process is used to tune the emission wavelength by heaters, then the emission wavelength can be adjusted, but the response time becomes longer exceeding one millisecond
Solution Approach 1:
The patent applies preliminary action by supplying pre-emphasis power to the heater before the actual wavelength re-tuning is needed. This pre-heating or pre-cooling action prepares the semiconductor material in advance, so that when the re-tuning command is given, the wavelength can be adjusted much faster since the thermal mass is already partially prepared. This directly addresses the slow thermal response time by performing part of the thermal work beforehand.
2Loss of time
If pre-emphasis power is supplied to the heater, then the stabilization time is reduced to 460-650 microseconds, but the power consumption increases
Solution Approach 1:
The patent implements periodic action by supplying power to the heater in distinct phases: first a pre-emphasis power phase for a predetermined time period, then a second power phase. This time-division power supply strategy allows the system to achieve fast wavelength re-tuning (460-650 microseconds stabilization) by concentrating energy delivery when most needed, rather than using continuous high power, thus managing overall power consumption while achieving rapid response.
3Adaptability or versatility
If the power is varied from first power Pa to second power Pb, then the emission wavelength is re-tuned, but the thermal inertia causes delay in wavelength stabilization
Solution Approach 1:
The patent overcomes thermal inertia by applying preliminary action through pre-emphasis power supply. Before the actual power transition from Pa to Pb, the heater receives pre-emphasis power for a predetermined time period, which starts the thermal change process early. This compensates for the thermal inertia of the semiconductor material, reducing the delay in wavelength stabilization from over 1 millisecond to 460-650 microseconds.
Solution Approach 2:
The patent applies beforehand cushioning by using the pre-emphasis power to partially compensate for the expected thermal delay. The pre-emphasis power prepares the thermal state of the semiconductor material in advance, cushioning against the inertial delay that would otherwise occur during the power transition from Pa to Pb. This ensures faster wavelength stabilization despite the inherent thermal mass of the system.
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
The approach significantly reduces the time to stabilize the emission wavelength, with the pre-emphasis technique shortening the stabilization period to around 460-650 microseconds, compared to 10-1300 microseconds without pre-emphasis, making the re-tuning process more efficient.
Implementation Method 1
The t-LD includes a heater to tune the emission wavelength thereof by being supplied with power
Implementation Method 2
the thermal process inherently shows a longer response from the application of heat to the variation of the refractive index of the semiconductor material
Data Source
AI summary
A laser apparatus for tuning the emission wavelength of a wavelength tunable laser diode will be described. The apparatus includes a tunable LD with heaters to tune the emission wavelength of the tunable LD, and a controller to control the power supplied to the heaters. A feature of the laser apparatus is that the controller supplies pre-emphasis power to the heaters before the supplement of the power corresponding to the re-tuned emission wavelength to accelerate the stability of the temperature of the heaters.