What is a Laser oscillator?

A laser is coherent light with excellent directivity and monochromaticity, and an oscillator consists of a medium, an excitation source, and a resonant mirror. Together these three parts are called a resonator. Based on the difference in the medium used for the oscillator, it can be divided into gas lasers, solid lasers, liquid lasers, semiconductor lasers, fiber lasers, and so on. Light transmission methods include CW (continuous wave) oscillation, pulse oscillation, and Q-SW (Q switch) pulse oscillation.

1. Excited states and transitions
The operation of a laser oscillator begins by bringing the atoms (or molecules) of the laser medium into an excited state. When an excitation source (lamp or laser semiconductor) illuminates a laser medium, atoms transition from a low energy state to a high energy state, and this high energy state is the excited state. This excited state is unstable, and the atom emits light corresponding to the energy difference when returning to a lower energy state. This phenomenon is called natural radiation. Furthermore, when excited atoms and molecules are irradiated with light of a specific wavelength, a phenomenon occurs in which they emit light in proportion to the intensity of the light. This is called stimulated emission.

2. Light Enhancement
The emitted light is reflected by a resonant mirror and returned to the laser medium. This process stimulates the emission of even more light, increasing the intensity of the light. This round trip is repeated many times, and when the light intensity reaches a certain level, the laser beam is oscillated externally through the partially transmitting mirror.

3. Structure of laser oscillator
A laser oscillator consists of an excitation source (e.g. a lamp or a laser semiconductor) and a cavity (the part that increases the intensity of the light). A resonator consists of a laser medium (a solid material such as a gas or a crystal) and a resonating mirror. Structurally, the excitation source is positioned to illuminate the laser medium, which is sandwiched between resonant mirrors on both sides. One side of this resonant mirror is a partially transmitting mirror, and the other is a fully reflecting mirror.

4. Others
pulse oscillation
Pulse oscillation is a method in which the laser output changes with time. Laser welding forms intermittent beads. This makes it possible to suppress the amount of heat input during welding as a whole, and to reduce thermal deformation of the workpiece.

Q-SW pulse oscillation
Q-SW (Q-Switched) pulse oscillation is a method that generates a high-power laser by waiting until sufficient population inversion occurs within the laser medium and then oscillating the laser all at once. This method is used for precision micromachining and hole machining of electronic and semiconductor components, etc.

CW oscillation
CW (Continuous Wave) oscillation is a method of oscillating a continuous wave laser. The output does not change over time and remains constant in intensity. When used in laser welding, the laser is irradiated continuously, so the welded area is integrated, allowing for highly airtight welding with no gaps.

Application of Laser oscillator

Lasers are used in a variety of fields, from military applications to consumer applications such as home appliances. Lasers suitable for the purpose are used based on their characteristics such as laser output and wavelength. Lasers are used in familiar situations in the following situations.

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