Second-harmonic generation of SESAM Q-switched microchip lasers
Penttinen, Antti (2023)
2023
Teknis-luonnontieteellinen DI-ohjelma - Master's Programme in Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2023-05-22
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202305175898
https://urn.fi/URN:NBN:fi:tuni-202305175898
Tiivistelmä
Pulsed laser sources are vital for a wide range of applications throughout the daily life. They are the key components in data transfer, medical use, industry as well as in variety of microscopic and spectroscopic applications. Novel microscopic and spectroscopic applications, such as photoacoustic microscopy or time-gated Raman spectroscopy require very specific pulsed laser sources. Even further, for many of these novel applications to reach a mature phase and foothold in our society, the light sources in use must come with affordable cost and compact footprint.
The optical properties required in many applications feature a combination of short pulses, high pulse repetition rates, high energies and suitable operation wavelengths. Many of these properties define the application measurement time or imaging depth and thus the right combination of these is vital.
For many novel applications requiring specific pulsed lasers, the options tend to be rather limited. Some solutions offer the required pulse repetition rates, enabling imaging speed and resolution, but are limited in pulse peak power, not generating imaging depth or targeted phenomena. Others can offer the correct optical parameters but the size or cost of such systems limits the applications. This issue of right combination of pulse parameters with a suitable technology platform was at the heart of this master thesis, with the focus on enabling novel imaging methods in the microscopic and spectroscopic applications.
This thesis focuses on the development of a compact microchip laser sources at 1534 nm with optical properties targeted for photoacoustic microscopy use. Lasers studied take advantage of a semiconductor saturable absorber mirrors (SESAM) technology to offer a unique combination of parameters with ns pulse duration, high repetition rate from tens of kHz to hundreds of kHz and kW pulse peak power. These lasers were frequency doubled to 767 nm using second harmonic generation in periodically poled lithium niobate (PPLN) to offer novel wavelength regions with suitable pulse parameters.
The optical properties required in many applications feature a combination of short pulses, high pulse repetition rates, high energies and suitable operation wavelengths. Many of these properties define the application measurement time or imaging depth and thus the right combination of these is vital.
For many novel applications requiring specific pulsed lasers, the options tend to be rather limited. Some solutions offer the required pulse repetition rates, enabling imaging speed and resolution, but are limited in pulse peak power, not generating imaging depth or targeted phenomena. Others can offer the correct optical parameters but the size or cost of such systems limits the applications. This issue of right combination of pulse parameters with a suitable technology platform was at the heart of this master thesis, with the focus on enabling novel imaging methods in the microscopic and spectroscopic applications.
This thesis focuses on the development of a compact microchip laser sources at 1534 nm with optical properties targeted for photoacoustic microscopy use. Lasers studied take advantage of a semiconductor saturable absorber mirrors (SESAM) technology to offer a unique combination of parameters with ns pulse duration, high repetition rate from tens of kHz to hundreds of kHz and kW pulse peak power. These lasers were frequency doubled to 767 nm using second harmonic generation in periodically poled lithium niobate (PPLN) to offer novel wavelength regions with suitable pulse parameters.