Carbon dioxide (CO₂) Lasers

Carbon dioxide (CO₂) Lasers Latest News

Physicists in the US have demonstrated a novel technique to detect radioactive materials remotely using carbon dioxide (CO₂) lasers.

About Carbon Dioxide (CO₂) Lasers

• The first CO₂ laser was developed by Indian-American scientist Prof. C.K.N. Patel.
• It is a four-level molecular gas laser that operates using vibrational energy states of CO₂ molecules.
• Highly efficient, producing high-power continuous or pulsed output.
• Structure: A CO₂ molecule consists of one carbon atom at the center and two oxygen atoms on either side. It vibrates in three independent modes:
  • Symmetric Stretching Mode: Oxygen atoms move simultaneously towards or away from the fixed carbon atom.
  • Bending Mode: Carbon and oxygen atoms vibrate perpendicular to the molecular axis.
  • Asymmetric Stretching Mode: Oxygen atoms move in one direction, while the carbon atom moves in the opposite direction.
• Principle of CO₂ Laser: The laser transition occurs between vibrational energy states of CO₂ molecules. Energy is transferred from excited nitrogen (N₂) molecules to CO₂, achieving the population inversion necessary for laser action.

Characteristics of CO₂ Laser

• Type: Molecular gas, four-level laser.
• Active medium: Gas mixture of CO₂, N₂, and He.
• Pumping Method: Electrical discharge.
• Optical Resonator: Concave mirrors.
• Power Output: Up to 10 kW.
• Nature of Output: Continuous wave (CW) or pulsed wave.
• Wavelength: 9.6 μm & 10.6 μm (Infrared region).

How Does the Detection Work?

• Radioactive decay & ionisation: When a material undergoes radioactive decay, it emits charged particles (alpha, beta, or gamma rays) that ionize the surrounding air, creating plasma.
• Avalanche effect: The free electrons in plasma gain energy and collide with other atoms, releasing more electrons. This self-sustaining process is called avalanche breakdown and leads to a chain reaction of ionization.
• Laser characteristics: Researchers used a carbon-dioxide (CO₂) laser emitting long-wave infrared (LWIR) radiation at 9.2 micrometres. The longer wavelength reduces unwanted ionization and improves sensitivity.
• Detection mechanism: The laser accelerates seed electrons in the plasma, creating microplasma balls. These microplasmas generate a measurable optical backscatter that can be detected and analyzed.
• Fluorescence imaging: Used to analyze the plasma formation dynamics and understand the distribution of seed electrons.
• Mathematical model: Developed to predict backscatter signals based on plasma seed densities.
  • Validation: The model accurately reproduced experimental results, confirming the reliability of the detection technique.

Advancements in Detection Range

• Alpha particles: Successfully detected from 10 meters away (10x improvement over previous methods).
• Gamma rays (Cs-137): Could potentially be detected from 100 meters away by scaling up laser optics.

Carbon dioxide (CO₂) Lasers FAQs

Q1: What is a Carbon Dioxide (CO₂) laser?
Ans: A CO₂ laser is a gas laser that uses a mixture of carbon dioxide, nitrogen, and helium to produce infrared light, widely used in industrial and medical applications.

Q2: What are the applications of CO₂ lasers?
Ans: CO₂ lasers are used in cutting, welding, engraving, and medical treatments such as laser surgery and skin resurfacing.

Q3: Why are CO₂ lasers preferred for industrial cutting?
Ans: CO₂ lasers have high power efficiency and precision, making them ideal for cutting and engraving metals, plastics, and other materials.

Q4: What is the wavelength of a CO₂ laser?
Ans: The wavelength of a CO₂ laser is around 10.6 micrometers (infrared range), which is ideal for heating and cutting applications.

Source: TH