Optical parametric oscillator (OPO)

What Is an Optical Parametric Oscillator (OPO)?

An optical parametric oscillator (OPO) is a nonlinear optical device that produces coherent light output at a wavelength that is different from the input wavelength. The device relies on the process of parametric amplification, which occurs when an incident photon is converted into two photons of lower energy. This conversion process is made possible by a nonlinear optical crystal that is placed inside the OPO cavity. The OPO was first proposed in the 1960s and has since found numerous applications in science and industry.

How Does an OPO Work?

The OPO is a three-mirror resonator that consists of a nonlinear optical crystal, a pump laser, and two mirrors that form the resonant cavity. The pump laser provides the energy necessary to create the parametric amplification process, which generates two lower-energy photons that are emitted in different directions. One of the photons is the signal photon, which is the output of the OPO, and the other is the idler photon, which is typically discarded. The signal photon can be tuned to any wavelength within the transparency range of the nonlinear crystal by adjusting the angle of the mirrors or the wavelength of the pump laser.

Applications of OPO: Examples

The OPO has numerous applications in fields such as spectroscopy, microscopy, and telecommunications. One example is in the field of biomedical imaging, where OPOs are used to generate tunable, high-power infrared light that can penetrate deep into tissue. This allows for non-invasive imaging of biological samples, such as living cells and tissues. Another example is in the field of quantum optics, where OPOs are used to generate entangled photons for quantum communication and quantum computing applications. OPOs are also used in materials processing, environmental sensing, and laser ranging.

Advantages and Limitations of OPO Technology

One of the main advantages of the OPO is its ability to generate tunable, coherent light at wavelengths that are not easily accessible with other laser technologies. This makes OPOs ideal for a wide range of applications that require specific wavelengths, such as spectroscopy and imaging. OPOs are also relatively compact and efficient, making them suitable for use in portable and remote sensing applications.

However, OPOs also have some limitations. The tuning range and output power of an OPO are limited by the properties of the nonlinear crystal and the pump laser. The efficiency of an OPO also depends on the quality of the resonant cavity and the stability of the pump laser. OPOs can also be sensitive to environmental factors, such as temperature and vibration, which can affect their performance. Overall, the OPO remains a versatile and powerful tool for generating tunable, coherent light in a wide range of applications.