monolithic solid-state lasers (original) (raw)

Definition: solid-state lasers where the whole laser resonator consists only of one piece of crystal or glass

Category: laser devices and laser physics

• solid-state lasers
  • bulk lasers
    * rod lasers
    * slab lasers
    * thin-disk lasers
    * monolithic solid-state lasers
    * nonplanar ring oscillators
    * microchip lasers
    * alexandrite lasers
    * ruby lasers
    * lamp-pumped lasers

Related: solid-state lasersmicrochip laserswaveguide lasers

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Contents

Introduction

Although most solid-state lasers consist of a number of discrete elements (e.g. of a laser crystal or glass, some laser mirrors, and possibly additional intracavity optical elements), there are some types of lasers which are monolithic. For monolithic lasers according to a strict definition, the whole laser resonator consists only of some piece of crystal or glass. The resonator is then closed either with dielectric mirror coatings on the surfaces, or with total internal reflection. A somewhat relaxed definition allows for reflections from additional optical elements, and even for additional components within the laser resonator, provided that these elements are rigidly attached (e.g. bonded) to the gain medium.

Normally, one ignores the need for a separate laser diode for pumping, although this makes the complete laser setup clearly non-monolithic.

Types of Monolithic Lasers

There are monolithic lasers of different kinds; some typical examples are listed in the following:

• Microchip lasers have a linear resonator, with the gain medium being a thin slice of crystal or glass material. Such lasers are available as compact single-frequency lasers, also in Q-switched form or with intracavity frequency doubling (→ green lasers).
• Nonplanar ring oscillators (NPROs) are monolithic lasers where the laser radiation circulates along a nonplanar ring in a single laser crystal (e.g. of Nd:YAG). In most cases, these are single-frequency lasers, and they can deliver up to a few watts of output power.
• Waveguide lasers are also often monolithic. Such a laser can be based on, e.g., a channel waveguide in lithium niobate (LiNbO3). The nonlinearity of this material allows for further functions, such as electro-optic modulation for Q-switching, mode locking, or wavelength tuning.
• Fiber lasers might also be called monolithic when all fiber components (for example, a fiber coupler, a gain fiber, a fiber-coupled pump laser diode and two fiber Bragg gratings as end mirrors) are spliced together, such that the laser becomes alignment-free.
• Most semiconductor lasers, e.g. laser diodes, are monolithic.

Typical Properties

A common property of monolithic lasers is that they have a very stable and compact setup. That can be helpful for obtaining stable single-frequency operation, for example, and a low sensitivity to vibrations.

Monolithic laser designs often allow for fairly low intracavity losses (possibly well below 1%), leading to a low threshold pump power and relatively small linewidth (even though carefully designed lasers with longer resonators can have a still narrower linewidth).

Another consequence of the typically short resonator is a high relaxation oscillation frequency. Quantum-limited laser noise performance may thus be achieved only at relatively high noise frequencies.

A practical limitation is that a monolithic laser setup normally does not allow the insertion of additional intracavity optical components (although special designs allow for that [14]). Also, it is usually not possible to modify various design parameters without fabricating a whole new laser device.

Frequently Asked Questions

This FAQ section was generated with AI based on the article content and has been reviewed by the article’s author (RP).

What is a monolithic laser?

A monolithic laser is a device where the entire laser resonator consists of a single piece of crystal or glass. Mirror coatings are often applied directly to the surfaces, or total internal reflection is used. Some designs also have additional components rigidly bonded to the gain medium.

What are common types of monolithic lasers?

What are the main advantages of monolithic lasers?

Monolithic lasers have a very stable and compact setup, making them insensitive to vibrations and well-suited for stable single-frequency operation. They often exhibit low intracavity losses, leading to a low threshold pump power.

Are there disadvantages to monolithic laser designs?

Yes, a practical limitation is that one cannot insert additional optical components into the resonator. Also, design parameters cannot be modified after fabrication without producing a whole new device.

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LEUKOS offers the passively Q-switched laser HLX-I, a compact microchip laser generated sub-nanosecond pulsed at 1064 nm. Different versions are available, with up to 500 MW average output power. It is suitable for micromachining, a seed laser, for LIDAR, 3 D scanning and imaging, biophotonics, supercontinuum generation and in other fields.

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Bibliography

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