Single-Frequency lasers (also known as single wavelength) are perfect for a wide range of different scientific applications and research. They operate under a single resonator mode (TEM) which produces a beam of laser light that has a very narrow line width and a very low noise amplitude. This means that it is is a very specific laser which will have little to no variation in the actual frequency (nanometer). For example, and single frequency 457nm laser (depending on parameters) should be 457nm +/- 1nm at the most. Anything beyond that where the beam can emit frequencies that exceed this narrow wavelength width, will not be considered single frequency.
Many low-power laser diodes are suitable for single-frequency outputs because of the way in which resonator modes (TEM) are outputting optical power. These units can also be rather sensitive to other varieties of optical or light feedback, meaning that even a small amount of variation can change the nature of the emitting laser beam. This can change the noise amplitude and phase noise or intensity noise, meaning that if they are not manufactured to these very specific parameters well, there could be some flaws in the output. Single frequency lasers must therefore be thoroughly protected from reflection in order to maintain the integrity of the specific frequency nanometer.
Here are some common types of single-frequency lasers:
- DPSS lasers (Diode-pumped solid-state lasers): these are a common form of laser (even some laser pointers may utilize this technology) and they can be designed to produce a single frequency mode. Strengths can be incredibly high using this method at over many watts with a low line-width, hence the “single wavelength” demarcation.
- Fiber Coupled or Fiber Lasers: very narrow line-widths of as low as a few kilohertz is possible using specific fiber optics and can be developed as distributed feedback lasers as the feedback is distributed through the fiber. The longer the fiber cable the more distribution and henceforth low linedwidth.
- Laser Diodes: lower power laser diodes often emit a single frequency. They can then be extended with fiber cables (single-mode). Typically the powers will be lower than a DPSS unit.
- Q-switch vs. Continuous: continuous wave is most common when it comes to single-frequency lasers, however, Q-switched units are possible where a clean pulse is produced with low noise through the output mechanism.
The variations of scientific single-frequency lasers that is available today has grown dramatically in even just the past 5 years. Where as before wavelengths would have to range from 305nm-2200nm, nowadays (2019) frequencies can be selected in a wider range from 305nm – 4400nm. This means there is more room for greater specificity and range when conducting various types of scientific and laboratory research with single wavelength lasers.
Applications For Single-Mode Lasers
Here are a few of the areas of research and expertise where a single wavelength laser is suitable.
- High-resolution Laser Spectroscopy
- Optical Fiber Laser Communications
- Optical Metrology
- Coherent Beam Combining
- Frequency Conversion (Nonlinear)
- Driving Resonance Cavities
Be sure to know what sort of specifics you need to conduct your research properly before choosing the laser you’ll be using. Costs can vary greatly based on different needs that you may have and therefore not every single frequency laser will be suitable for your research. If you have technical questions, ask them to build a body of information you can assess prior to buying a single frequency scientific research laser.