Learn More About VBG Laser Diodes
As opposed to diffraction gratings (made on the surface of an optical element) Volume Bragg Gratings are written on the inside of the material. Furthermore, the grating is usually placed not directly in front of the laser diode but after a collimating lens. In short, this is important for pumping of certain solid-state lasers, where the laser crystal exhibits efficient pump absorption only in a narrow wavelength range. Typically, the Volume Bragg Grating’s end faces are optically polished, with an anti-reflection coating applied, to help prevent parasitic reflections.
Volume Bragg Gratings Provide Wavelength Stabilized Laser Diodes:
A common use for Volume Bragg Gratings is the production of wavelength stabilized laser diodes. The addition of a VBG to a laser diode creates additional optical feedback to the diode laser, forcing it to emit laser light that is within the narrow optical bandwidth determined by the VBG. Basically, this means that the mean wavelength output of the laser diode is fixed, for all intents and purposes.
Without this feedback, the laser diode would be subject to wavelength shift due to temperature changes, as well as changes due to increasing age of the laser diode. Finally, this method allows for the reduction of total optical bandwidth from, say, a few nanometers, down to some fraction of a nanometer, which is beneficial to solid-state laser pumping, Raman spectroscopy, and other applications which require a narrow linewidth, wavelength stabilized laser diode.
Our VBG Laser Diode Products
Our Volume Bragg Grating Laser Diodes provide Narrow Linewidth, CW output in the Red and Near Infrared (NIR) spectral regions. Furthermore, these laser diodes provide up to 750mW for our Single-mode options and up to 400W for our Multimode options. Finally, we provide options for free-space or fiber-coupled output and package options, including TO-can, butterfly and more.
Volume Bragg Grating (VBG) Laser Diode Applications
Multimode vs Single-Mode Lasers for Raman Spectroscopy
The first question you should ask yourself when considering which type of laser to choose is whether you are doing microscopy or bulk sampling. If the answer to that question is microscopy, then you immediately should go with a single mode laser. Since the goal of any microscopy system is to produce the highest resolution image possible, the number one consideration should be how tightly can the laser beam be focused down. In optics, the M2 of a laser determines how small of a spot size can be achieved for a given microscope objective with an M2 of 1 being the best possible focus. Even though a perfect M2 of 1 can never be physically achieved, open beam single mode diode lasers can typically have a M2 < 1.5 and single mode fiber-coupled diode lasers have an M2 »1.05.
On the other hand, if you are performing bulk sampling the question becomes a bit more complicated. If you are looking to measure non-absorbing, highly uniform samples, with smooth surface texture, and an amorphous structure, such as a liquid or a fine powder then single mode lasers are still a good choice. While this may seem like an overly specific example, it’s actually fairly common for many educational and “fit-for-purpose” applications.
Read the full article here.
Stabilized vs Unstabilized 976 nm Laser Pump Lasers
Technically speaking fiber lasers are a specific subset of diode-pumped solid-state lasers (DPSS), even though their unique qualities tend to get them placed in their own category. As a diode-pumped laser, fiber lasers take advantage of the shape of the dopant’s absorption spectrum in order to maximize the efficiency by pumping at the wavelength of peak absorption.
The most well-known example of this is the 808 nm absorption peak on neodymium (Nd) which is exploited in traditional Nd:YAG /Nd:YVO DPSS lasers. In this blog post we are going to take a look at two most commonly used fiber laser dopants erbium (Er) and ytterbium (Yb) which both have a strong absorption peak at 976 nm, but who’s bandwidths vary dramatically causing one to require a wavelength stabilized diode pump.
Read the full article here.
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