Analysis of the Effects of Environmental Temperature on the Stability of Laser Frequency

Fluctuations in ambient temperature can directly affect the frequency stability of lasers, and thus affect applications such as precision measurement and communication systems.From the perspective of thermal expansion of the laser and changes to the refractive index of materials, the book explores how to improve a laser system's resistance to interference through temperature control technology and optimal structural design.

Why does temperature affect the laser's frequency?

The laser equipment we use in our daily lives, such as spectrometers in laboratories or fiber-optic communications systems, have core components that are very sensitive to temperature.A change in temperature will cause the material of the laser to expand or contract, and this will also affect the refractive index of the optical components.In simple terms, just as steel railroad tracks can buckle in summer, the "optical path" of a laser can be deformed by temperature fluctuations, ultimately leading to an unstable output frequency.

The practical problem of temperature fluctuations.

Errors in precise measurements.

In a laboratory, if the wavelength of a laser used for measuring distances or calibrating atomic clocks is off by just 0.1 %, the results could be off by a thousand miles.Last year, a university research team encountered a similar problem. A malfunctioning air conditioner caused the temperature in the lab to rise 3 ° C, and their interferometer data "drifted." Only after repeating the experiment three times did they discover the source of the problem.

The quality of communications signals declines.

If heat dissipation is not properly designed for fiber-optic communication base stations, the laser frequency will shift as the temperature of the cabinet rises in the summer heat.At this time, the rate of errors in data transmission rises dramatically. A drop in the transmission speed is just a minor inconvenience; in serious cases, it can even cause the link to be cut off.

How can they cope with the problems of temperature?

The laser is given a "constant-temperature jacket.

The mainstream solution is to add temperature control devices to the core module.For example, by using a semiconductor cooler in combination with a proportional-integral-derivative (PID) algorithm, temperature fluctuations can be kept within ± 0.1 ° C.Some high-precision equipment even uses double-layer insulation, like a thermos bottle, to wrap around the laser.

Choosing the right materials is very important.

Engineers found that the use of zero-thermal-expansion glass (for example, ULE) for the laser cavity could better withstand temperature changes.One laser manufacturer switched to this material, and the frequency stability of its lasers increased by a factor of five in the 15-35 ℃ temperature range.

Real-time monitoring is indispensable.

He suggested that a network of temperature sensors should be installed in the system in order to monitor critical areas such as the laser crystal and the mirrors.The system also employs adaptive compensation algorithms, which automatically adjust the drive current or optical path when the temperature is detected to be abnormal.Last year Huawei unveiled a 5G base-station laser module that uses this trick, remaining stable even in extreme temperatures.

Tips for daily maintenance.

Never underestimate the importance of environmental temperature control. The temperature in a testing lab should be kept at 22 ± 2 ° C, and industrial equipment should be kept away from heat sources and areas where air circulation is poor.If there is an abnormality in the laser output, check the temperature records first. Often the problem is something as small as a malfunctioning air conditioner or a dusty cooling fan.If you encounter a sudden temperature change, remember to wait until the equipment has fully warmed up before recalibrating. If you try to use it when it's still cold, you'll damage the machine.