OPO laser testing optical components

Optical parametric oscillator laser tests fibers and components to characterize the spectral response of optical components, thereby providing a competitive advantage in the optical industry.

OPO lasers have long been used in complex testing and measurement applications, such as mass spectrometry, photoacoustic imaging, and spectroscopy. Now, these "tunable" pulse lasers are being used to facilitate a series of tests at different wavelengths to identify and quantify the performance of optical components such as fiber bundles, filters, lenses, and coated mirrors.

According to design, most optical components reflect, filter, or transmit specific wavelengths or wavelength ranges. Therefore, it is crucial to test component materials and coatings to ensure that the product operates as expected. The more precise these tests are, the higher the product quality, and manufacturers can translate this factor into a competitive advantage.
            
Since the testing conditions should be replicated or simulated in actual operating environments, lasers can be used to provide narrow band, pulse duration, and power levels to determine the spectral response of optical components.
These tests provide optical component manufacturers with key information related to factors such as absorption, scattering, and other optical properties. Damage testing becomes crucial in determining whether a given optical material will be damaged at different wavelengths. The coating may also be damaged at specific wavelengths, leading to performance issues.

Due to the wide testing range, it would be advantageous if the laser could be tuned to any desired wavelength. This provides greater flexibility and reduces complexity, so manufacturers can ensure that the performance of optical products meets expectations.

Advantages based on pulses
The use of pulse based lasers can bring significant benefits. Although continuous wavelength lasers are an inexpensive solution for testing optical materials, they cannot provide a wide range of high-resolution wavelengths, and the peak power they can generate is limited.

Pulsed lasers generate high-intensity light bursts, which can be used to determine whether the transmission characteristics of optical materials or coatings are affected. Optical component manufacturers may wish to test this to determine whether high-intensity light can cause damage, such as nonlinear effects or cross wavelength spectral exposure to sunlight or photobleaching. The power of a continuous wave laser is not sufficient for this level of damage testing.

When single wavelength pulse based lasers are needed, Nd: YAG lasers are an ideal choice because they are relatively inexpensive and easy to use. The 1064 nm laser can also be modified with additional hardware to operate at its other harmonic frequencies: 213, 266, 355, and 532 nm. Although this provides five defined wavelengths for testing, each modification incurs additional costs.

There is a gap between wavelengths, with a large jump between 1064 nm and 532 nm. Each of these harmonics will increase the cost. Optical component manufacturers will want to know how their products perform at wavelengths between these harmonics.

A more universal and high-resolution option is the OPO laser, which can be tuned to specific wavelengths over a wide spectral range. In this method, OPO converts the fundamental wavelength of the pulse mode Nd: YAG to a selected frequency. Opotek and other manufacturers have developed a range of OPO technologies to ensure easy production of multiple wavelengths from deep ultraviolet to mid infrared.

For example, an OPO laser can be adjusted to wavelength resolution by simply inputting a number, such as 410, 410.1, or 410.2 nanometers. Some tests require high-resolution wavelengths, but with broadband light sources, you may not be able to achieve them.

Many optical components are sensitive to certain wavelengths, and destructive damage testing determines the limits that materials can withstand. The laser induced damage threshold test is an example.

Certain wavelengths can trigger photochemical reactions in optical materials, altering their molecular structure or chemical composition and reducing their effectiveness. Some materials can absorb light of specific wavelengths, leading to local heating and potential thermal damage. When the intensity of light exceeds the damage threshold of the material, it can cause melting, evaporation, cracking, or other forms of physical damage.

Fiber optics and components typically have protective coatings, which are also susceptible to damage at certain wavelengths. One of the most common applications is fiber optics, which can cause various forms of damage when exposed to high-intensity lasers for a long time. To test the fiber bundle, laser is transmitted from one end to the other to evaluate the performance and characteristics of the fiber.

For example, to determine peak power, pulse based OPO lasers can provide concentrated energy bursts in a short period of time in nanoseconds. Due to the fact that peak power is calculated by dividing the energy of a single pulse by the pulse duration, OPO lasers can provide energy at the megawatt level, while continuous wave lasers are at the milliwatt level.

Given the wide range of potential testing types at different wavelengths, optical component manufacturers should consider the advantages of pulse based OPO lasers. The flexibility and resolution provided are ideal choices for determining the absorption, transmission, and reflection characteristics of materials and coatings, as well as for damage testing. By doing so, manufacturers can ensure that the performance of optical products meets expectations, thereby providing a competitive advantage in the optical industry.

Source: Laser Net