Question

Three main components of a laser are the pump, active material, and cavity. Four main types of lasers are gas lasers, semiconductor lasers, dye lasers, and solid state lasers. Match the example component with the best description of the type of component and type of laser it is found in specified. (Each answer will be used once.) $$ \begin{array}{|l|} \hline \text { Example Component } \\ \hline \text { 1. Edges of a AlGaAs crystal } \\ \hline \text { 2. Rhodamine } 6 \text { G liquid solution } \\ \hline \text { 3. External mirror made of } \mathrm{SiO}_{2} \text { glass coated with } \\ \text { aluminum } \\ \hline \text { 4. Battery of a laser pointer } \\ \hline \text { 5. } \mathrm{SiO}_{2} \text { glass doped with } 1 \% \text { Er atoms } \\ \hline \text { 6. } \mathrm{CO}_{2} \text { gas in an enclosed tube } \\ \hline \text { 7. Pn junction made from InGaAs } \\ \hline \text { 8. Argon ion laser used to supply energy to excite } \\ \text { electrons of a Ti doped Sapphire } \\ \hline \hline \text { Description } \\ \hline \hline \text { A. Cavity of a semiconductor laser } \\ \hline \text { B. Cavity of a gas laser } \\ \hline \text { C. Active material of a semiconductor laser } \\ \hline \text { D. Active material of a gas laser } \\ \hline \text { E. Active material of a dye laser } \\ \hline \text { F. Active material of a solid state laser } \\ \hline \text { G. Pump of a semiconductor laser } \\ \hline \text { H. Pump of a solid state laser } \\ \hline \end{array} $$

Short answer

1A, 2E, 3B, 4G, 5F, 6D, 7C, 8H.

Step-by-step solution

Edges of a AlGaAs crystal

The edges of an AlGaAs (Aluminum Gallium Arsenide) crystal acts as the cavity for a semiconductor laser. It provides the structure for reflecting photons back into the device to stimulate further emission. **Matched Description: A. Cavity of a semiconductor laser**

Rhodamine 6 G liquid solution

Rhodamine 6 G is a dye used as the lasing material in dye lasers. It acts as the active material because it emits light when stimulated by an energy source. **Matched Description: E. Active material of a dye laser**

External mirror made of SiO₂ glass coated with aluminum

An external mirror made of SiO₂ glass coated with aluminum is used in gas lasers to form part of the optical cavity, which confines and reflects the light back into the lasing medium. **Matched Description: B. Cavity of a gas laser**

Battery of a laser pointer

The battery of a laser pointer supplies the necessary electrical energy to stimulate the active medium. It serves as the pump in a semiconductor laser, providing power for the lasing process. **Matched Description: G. Pump of a semiconductor laser**

SiO₂ glass doped with 1% Er atoms

This is a solid-state laser material, where SiO₂ glass doped with erbium atoms acts as the active material due to its capability to emit coherent light when excited. **Matched Description: F. Active material of a solid state laser**

CO₂ gas in an enclosed tube

CO₂ gas functions as the active material in a CO₂ gas laser due to its ability to emit light when electrically excited. **Matched Description: D. Active material of a gas laser**

Pn junction made from InGaAs

The Pn junction made from InGaAs (Indium Gallium Arsenide) serves as the active material in a semiconductor laser. It emits light when current flows across it. **Matched Description: C. Active material of a semiconductor laser**

Argon ion laser used to supply energy to excite electrons of a Ti doped Sapphire

An argon ion laser is commonly used to pump the Ti (titanium) doped sapphire in solid-state lasers, providing the initial energy required for laser action. **Matched Description: H. Pump of a solid state laser**

Key concepts

Laser Types

Lasers come in various forms, each with unique characteristics determined by their construction and the type of material in use as the active component. Here are the four main types of lasers highlighted in the exercise:

• Gas Lasers: These use a gas or a mixture of gases as the active material. A common example is the \( \text{CO}_2 \) laser, which is efficient and widely used in industrial applications.
• Semiconductor Lasers: These are compact and efficient, using materials like \( \text{InGaAs} \) (Indium Gallium Arsenide) as the active medium. They're often found in devices like laser pointers and optical communication equipment.
• Dye Lasers: These utilize liquid solutions of dyes, such as Rhodamine 6G, that emit light when pumped with an external energy source. They offer tunable wavelengths, making them versatile but often less stable than solid-state lasers.
• Solid-State Lasers: Solid crystals or glass materials doped with ions, such as Erbium-infused \( \text{SiO}_2 \) glass, serve as the active medium. These are used in applications ranging from medical surgeries to cutting and welding in industrial settings.

Understanding the different types of lasers helps highlight their suitable applications based on design and material.

Active Material

The active material is the heart of a laser, determining its energy output and the wavelength of the light emitted. Various lasers utilize different types of active materials:

• In gas lasers, such as a \( \text{CO}_2 \) laser, the gas acts as the active material. Here, the gas molecules get excited and emit photons of a specific wavelength.
• In semiconductor lasers, materials like \( \text{AlGaAs} \) and \( \text{InGaAs} \) form the core. These semiconductors emit light when electrons within them are re-energized or stimulated.
• For dye lasers, liquid dyes such as Rhodamine 6G serve as the active medium. When external light energy pumps the dye molecules, they become excited and release light at various tunable frequencies.
• Solid-state lasers utilize crystal or glass doped with ions. For instance, \( \text{SiO}_2 \) glass doped with Erbium emits light when excited, allowing various innovative uses across different fields.

This diversity in active materials allows lasers to adapt practically every technology, from cutting-edge therapeutic uses to daily consumer electronics.

Cavity

A laser's cavity, also known as the optical resonator, plays the crucial role of maintaining the amplification of emitted photons, leading to a coherent beam of light. Each laser type requires a uniquely designed cavity to maximize efficiency and output.

• In semiconductor lasers, the cavity often forms from the edges of the semiconductor material, like an \( \text{AlGaAs} \) crystal. This cavity confines the emitted photons, allowing them to bounce back and forth, further stimulating light amplification.
• For gas lasers, external mirrors typically form vital parts of the cavity. For example, a mirror made of \( \text{SiO}_2 \) glass coated with aluminum reflects light inside a \( \text{CO}_2 \) laser, essentially forming part of its resonating structure.

The optical cavity's construction ensures the emitted light is pure, coherent, and directed, making laser output powerful and precise for a range of applications.

Pump

A laser's pump supplies the necessary energy to excite the active medium, initiating the lasing process. The type of pump varies based on the laser's design and intended use:

• In semiconductor lasers, electric currents often serve as the pump source. For example, a battery in a laser pointer supplies electrical energy to stimulate the semiconductor junction.
• Solid-state lasers frequently utilize another laser as a pump. An Argon ion laser might pump energy into a Ti (titanium) doped sapphire, providing the needed excitation for lasing.

Properly matching the pump to the active medium ensures efficient laser operation, which is critical for maintaining performance and achieving the desired laser effects.