Green Lasers

Deeper Dive into Green Lasers

Some Green Laser Applications

Some popular Green applications include Bathymetry, Thin Film Removal, Interferometry, Holography, Machine Vision, Confocal Fluorescence Microscopy, Flow Cytometry, DNA Sequencing, Optogenetics, PDT, Dental, and many others.

Gallium Nitride (GaN) Laser Diodes: Green, Blue, and UV Wavelengths

Semiconductor devices can be engineered to have a specific bandgap energy by combining various elements to form binary, ternary, and quaternary alloys.  These semiconductors can have their bandgap further tailored, varying the stoichiometry in ternary and quaternary semiconductors.  In our specific case, visible laser diodes can be produced from a combination of nitride materials, such as aluminum nitride (AlN), GaN, and indium nitride (InN), creating AlGaN and InGaN laser diodes for example.  The resultant alloy, typically referred to as simply ‘GaN’ in shorthand, can theoretically be combined using the following formulas Al_xGa_1−xN and Al_xIn_yGa_1−x-yN to form any bandgap which falls within the “banana,” shown in the figure to the right.

The Green, Blue & UV Laser Diode Revolution

In practice, the material science involved in stably producing laser diode structures with any arbitrary stoichiometry is far more challenging.  As stated earlier, for many years it was thought that these challenges would never be overcome, until 1996 when the first AlGaN laser diode was invented by Shuji Nakamura.  Nakamura’s work with GaN based semiconductor lasers and LEDs was so revolutionary that he was later awarded the Nobel prize in physics.  Over the past 20 years, the technology for making Gallium Nitride (GaN) Laser Diodes has matured into its own branch of optoelectronics.  These laser diodes are now available in wavelengths from 375 nm to 521 nm, with output powers exceeding 100 watts.

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Laser Alignment: HeNe Lasers, Methods, and Helpful Tips

Are you wondering how to align an infrared beam? Aligning an infrared wavelength laser can be tedious and frustrating since you’re dealing with an invisible beam. Therefore, the use of visible wavelength HeNe lasers in the red or green regimes proves to be quite helpful for actively visualizing your optical path during the alignment process. In the case of red wavelengths, the human eye’s sensitivity starts to drop quickly as the wavelength increases toward the infrared. So, choosing a shorter red wavelength (e.g., 630nm vs. 690nm) provides a much higher level of visibility, especially with high levels of ambient light. Some optical components may cause alignment issues when using specific wavelengths due to various wavelength-dependent dielectric coatings on optical lenses and other chromatic aberrations. Typically, these issues are only seen in optical lenses and not on reflecting mirrors. So, if your system involves optical lenses, be sure to note any conflicts with your lens coatings or substrate composition and the visible wavelengths you might use to align the optical system.

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High-Power CW Lasers for Holography, Interferometry & Spectroscopy

Critical Laser Source Requirements Common to Holography Applications

Wavelength – The final consideration when looking at lasers for holography is the wavelength needed for the best results. Security labels would be ineffective if they were recorded in the IR region, outside the range of the human vision. Many modern holographic images are created using multiple wavelengths – red, green, and blue – in order to produce a colored final image. Holographic applications that do not rely on the human visual range can utilize wavelengths outside the visible range. Data storage, for instance, would indeed benefit from shorter UV wavelengths, leading to higher information density.

Critical Laser Source Requirements Common to Raman Applications

Wavelength – The strength of the Raman signal is directly dependent on the wavelength of the laser source, where lower wavelengths will produce stronger Raman signals, as well as allowing for higher spatial resolution. It is important, however, to balance this observation with the occurrence of background fluorescence, prevalent in many materials throughout the UV-visible spectrum, and the possibility of sample damage at high energy. These effects most often cause a compromise in the wavelength of the source used, where longer wavelengths, such as 532 nm, 785 nm, and 1064 nm, in combination with highly sensitive detectors, allow for the widest range of samples to be measured.

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Lasers for Tattoo Removal

Black tattoos are the easiest to remove because they tend to absorb all visible and near infrared laser wavelengths, but colored tattoos add additional complexity to the laser selection process.  The difficulty arises because the full range of chromophores used in the different inks all have unique absorption properties, making it virtually impossible to choose a single wavelength.  For example, you cannot use a green laser to remove a green tattoo or a red laser to remove a red tattoo because the ink will inherently diffusely reflect the light instead of absorbing it.  To make matters worse when you get to more complicated colors such as purple which utilize a wide variety of pigments mixed, you may need to use multiple different wavelengths to remove the ink entirely.    One way that practitioners work around this issue is using second harmonic generation (typically via KTP), to double the efficacy of the process.  By placing the non-linear crystal into the laser’s delivery system without adding any filtration to block the fundamental, it is possible to excite the ink with two different wavelengths simultaneously.

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LIDAR Becoming the Future of Bathymetry

Because of the absorption spectrum of liquid water, 1064 nm and 532 nm lasers are typically used as the two transmission wavelengths for this application.  In this process, the 1064nm laser is first used to establish the reference level for the surface of the body of water, using standard TOF processing.  Once this reference level is determined, the system will then look at the TOF for the green laser minus the TOF for the 1064 nm laser pulse, to calculate the total depth.  It is important to note that the speed of light is much slower in water than in air, so it is necessary to take the index of refraction of water into consideration resulting in the following equation for depth, D = ( ΔT532 − ΔT1064) × C/2n.  In this equation ΔT532 and ΔT1064 represents the total TOF for the green and NIR laser pulses respectively and n is the index of refraction of water, which typically varies between 1.33 and 1.38 depending on the salt content.

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Key Laser Requirement for Bathymetric and Topographic LIDAR

As with most airborne topographic LIDARs, bathymetric systems share the same demand for compact, efficient, rugged, and industrial-grade laser sources. Bathymetric applications present an additional degree of complexity, strictly related to the transmitting medium, with shallow nearshore zones not-necessarily-clean or clear. Bathymetric systems can efficiently use only a limited range of possible wavelengths due to poor water penetration. While most topographic LIDARs employ infrared detectors and laser sources operating at 1064 nm, or the “retina-safe” wavelength of 1550 nm, those wavelengths would only be able to penetrate a few centimeters into the water.

Therefore, light absorption dictates that the ideal wavelength is approximately 440nm for clean water and some longer wavelength (~500nm) for impure scenarios, such as ocean water in the coastal zones, where chlorophyll plays a substantial role in absorbing blue light. High-peak-power, nanosecond, pulsed lasers, operating at 1064nm, efficiently generate 532nm radiation, utilizing a nonlinear optical process, known as second harmonic generation (SHG). Furthermore, the generation of green light by SHG of an infrared laser source has the advantage of utilizing well-synchronized, residual, unconverted light at the fundamental wavelength that could be used for the external surface identification. However, for a given required pulse energy at 532 nm, the commonly achieved SHG efficiency of 50% implies that higher pulse energy (by a factor of 2) is required for the laser source operating at the native wavelength of 1064 nm. Moreover, even assuming low water absorption at 532 nm, the transmission is still much lower than in air, thus further increasing the demand for pulse energy.

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Flow Cytometry: Application Basics, Source Requirements & Solutions

Flow cytometry is a method for simultaneously analyzing multiple physical properties of an individual cell as it flows through a beam of light in a fluid stream, including the cells size and fluorescence.   In practice, flow cytometry is essentially a combination of particle counting and fluorescence spectroscopy. Just as in traditional particle counting, these lasers must exhibit excellent pointing and power stability, and single-mode, low noise operation (typically free-space output). However, unlike conventional particle counting systems, the wavelengths must be chosen to match the excitation spectra of the available fluorophores. Typical wavelengths include 355nm, 405nm, 473nm, 488nm, 532nm, 553nm, 561nm, 594nm, 640nm and NIR, with output powers in the 25-500mW range. Additionally, since multiple lasers are being integrated into a single system, size, cost, and ease of integration all become significant factors in deciding which laser to choose.

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Expert Solutions for Your PCB Processing Applications

With our robust systems, you will be able to successfully tackle any PCB processing challenge, from cutting to marking, utilizing the same laser source. Whether needing selective material removal (e.g. solder resist film on copper, or gold on alumina), track interruption (short-circuit), in-situ micro-corrections of connection errors, component termination & separation, or barcode & data matrix marking, we have the right solution for you.

These solutions include a range of compact, air-cooled DPSS lasers with high-energy ns and sub-ns pulses. The single-unit design of these lasers allows for fast and easy replacement in the field, and in the example of the SOL Series – 532 nm green laser, each model shares the exact same mechanical footprint.

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New Dual-Wavelength Raman Probe Enhances Flexibility & Throughput

The most exciting, unique feature of this Raman probe is the dual-wavelength concatenation capability. There are other, standard configurations already on the market that offer two wavelengths (say 532 & 785nm dual-band). However, these devices require two separate spectrometers. Basically, they are just switching between the two bands, utilizing each wavelength for different samples with unique fluorescent characteristics. Now, this new design allows you to interrogate the whole band (fingerprint and stretch region) with a single spectrometer. No more switching.

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Micromachining

Compared with near-infrared lasers, 532nm lasers (green lasers) provide a number of benefits, namely a higher absorption coefficient in copper, gold, or silicon, for example. This allows you to operate the laser at less overall power, while simultaneously getting better quality results in your laser material processing. While the cost may be higher than that of a 1064 nm laser, for example, the benefits are worth the higher price point if quality is a concern.

See our Micromachining Laser page here with supporting blogs.

How Can We Help?

With over 25 years experience providing green lasers to various researchers and OEM integrators working in various markets and applications, and 1000s of units fielded, we have the experience to ensure you get the right product for the application. Working with RPMC ensures you are getting trusted advice from our knowledgeable and technical staff on a wide range of laser products.  RPMC and our manufacturers are willing and able to provide custom solutions for your unique application.

If you have any questions, or if you would like some assistance please Contact Us here. Furthermore, you can email us at [email protected] to talk to a knowledgeable Product Manager.

Alternatively, use the filters on this page to assist in narrowing down the selection of Green lasers for sale. Finally, head to our Knowledge Center with our Lasers 101 page and Blogs, Whitepapers, and FAQ pages for further, in-depth reading.

Finally, check out our Limited Supply – In Stock – Buy Now page: This page contains an ever-changing assortment of various types of new lasers at marked-down/discount prices.