Podcast
Questions and Answers
What are the three processes needed to produce a laser beam?
What are the three processes needed to produce a laser beam?
The original meaning of LASER stands for Light Amplification by the Stimulated Emission of Radiation.
The original meaning of LASER stands for Light Amplification by the Stimulated Emission of Radiation.
True
What is the difference between spontaneous emission and stimulated emission?
What is the difference between spontaneous emission and stimulated emission?
Spontaneous emission occurs when an electron in an excited state drops to a lower energy level randomly, emitting a photon. Stimulated emission occurs when an electron in an excited state is triggered by a photon of the same energy to drop to a lower energy level, emitting another photon with the same properties as the incoming photon.
Which of the following is NOT a common type of laser active medium?
Which of the following is NOT a common type of laser active medium?
Signup and view all the answers
What is population inversion?
What is population inversion?
Signup and view all the answers
What is the role of a metastable state in creating a laser beam?
What is the role of a metastable state in creating a laser beam?
Signup and view all the answers
How do pumping sources contribute to laser operation?
How do pumping sources contribute to laser operation?
Signup and view all the answers
What are the main components of a laser apparatus?
What are the main components of a laser apparatus?
Signup and view all the answers
Which of these is NOT a property of a laser beam?
Which of these is NOT a property of a laser beam?
Signup and view all the answers
What is the Doppler effect in relation to lasers?
What is the Doppler effect in relation to lasers?
Signup and view all the answers
What is a laser Doppler velocimeter and how does it work?
What is a laser Doppler velocimeter and how does it work?
Signup and view all the answers
Which of these is NOT a factor used to classify lasers according to their hazard level?
Which of these is NOT a factor used to classify lasers according to their hazard level?
Signup and view all the answers
What are the key differences between the two main types of laser therapy: low-level laser therapy (LLLT) and high-level laser therapy (HLLT)?
What are the key differences between the two main types of laser therapy: low-level laser therapy (LLLT) and high-level laser therapy (HLLT)?
Signup and view all the answers
Which of these is NOT an advantage of laser therapy?
Which of these is NOT an advantage of laser therapy?
Signup and view all the answers
What are the key differences between laser light and X-rays?
What are the key differences between laser light and X-rays?
Signup and view all the answers
Study Notes
Laser and Its Applications
- Lasers are a type of equipment that produces a narrow beam of light with a single wavelength (monochromatic).
- Originally, LASER was an acronym for Light Amplification by the Stimulated Emission of Radiation.
- Now, laser is used to identify the equipment and the light it produces.
Introduction
- Lasers produce a narrow beam of coherent light with a single wavelength, making it highly concentrated and parallel.
- The light from a laser is in phase meaning the waves are precisely aligned (coherent).
- Lasers use three key processes to generate a beam: stimulated emission, population inversion, and a pumping source.
Requirements for a Laser Beam
- Three components must be met for laser beam generation:
- Stimulated emission: A process where an atom in an excited state releases a photon, then another atom is stimulated to release a photon with the same characteristics.
- Population inversion: More atoms need to be in an excited state than in the ground state.
- Pumping source: The pumping source provides energy to excite atoms to a higher energy level.
1) Stimulated Emission
- Atoms have different energy levels
- Ground state (lowest energy)
- Excited states (higher energy)
- The atom transitions between these energy levels when it absorbs or emits photons.
- Stimulated emission occurs when an already excited atom releases a photon due to interaction with another photon, causing another atom to release a similar photon.
Absorption
- An atom in a lower energy level may absorb a photon.
- The energy of the photon must exactly match the difference in energy between the lower and higher energy levels.
Emission
- When an atom in an excited state drops to a lower energy level, it emits a photon.
- Spontaneous emission is when the drop occurs naturally, while stimulated emission occurs due to interaction with another photon.
a) Spontaneous Emission
- Emission occurs naturally after the electron spends a period of time in an excited state.
- The emitted photons are incoherent, meaning their phases vary inconsistently.
b) Stimulated Emission
- Emission happens earlier, during the electrons lifetime due to interactions with an external electromagnetic radiation.
- The emitted photons are coherent and have the same characteristics as the stimulating photon.
2) Population Inversion
- It's a process where a laser medium is excited to increase atom numbers in a higher energy state compared to the ground state
- Based on Boltzmann statistics, the number of atoms in different energy levels (E1 and E2) at a given temperature are calculated.
- "Normal population" means more atoms are in lower energy levels
- "Population inversion" means more atoms are in higher energy levels.
- Metastable state: An excited state characterized by a longer lifetime; this allows for enough time for a photon to stimulate further emission from excited atoms.
3) Pumping Sources
- Energy is added to the laser medium to excite atoms to higher energy levels, potentially leading to population inversion.
- Electric pumping: Suitable for gas lasers (narrow absorption band).
- Chemical reaction: Used to excite atoms.
Laser Apparatus
- A device producing a highly intense and parallel beam of coherent light
- For any laser, it should have three main components: active medium, pumping source, and optical resonator.
Active Medium/Types of Lasers
- Lasers are categorized by their active medium:
- Solid state (e.g., Ruby, Nd-YAG)
- Liquid (e.g., Dyes)
- Gas (e.g., He-Ne, CO2)
Ruby Laser (Example)
- A specific type of solid-state laser.
- Illustration shows the construction of a ruby laser, including the ruby rod, flash tube, and mirrors.
Laser Beam Properties
- Coherent (in phase)
- Monochromatic (single wavelength)
- Collimated (highly parallel)
- Intense (concentrated)
- Excellent frequency stability
- Small beam diameter (high coherence)
- Highly-focused energy
Doppler Effect
- Source moving toward the observer: Wavelength decreases, frequency increases, blue shift.
- Source moving away from the observer: Wavelength increases, frequency decreases, red shift.
Laser Doppler Velocimeter (LDV)
- Technique to measure instantaneous velocity of a flow field.
- Uses a monochromatic laser beam directed at a target.
- Reflected radiation is analyzed to determine object velocity based on wavelength changes, using an interference fringe pattern.
- Uses a Helium-Neon (He-Ne) or Argon ion laser as source with 10-20 watts of power.
Lasers and Hazards
- Lasers are classified by their potential for harm based on output power level and emitted wavelengths to define safety precautions.
- Class 1-1M (safe)
- Class 2-2M(safe with appropriate precautions)
- Class 3R(Restricted, hazardous with direct viewing)
- Class 3B (may cause eye damage with direct viewing)
- Class 4 (high power, both eye and skin burns and is a fire hazard)
Laser Therapy
- Uses specific wavelengths of light to stimulate healing.
- Patients do not feel pain during treatment.
- Aims to reduce inflammation and muscle fatigue, and to promote faster wound healing.
Laser Interaction Mechanisms
- Photochemical interaction: Chemical reactions involving photons. Examples include photosynthesis, melanin production, vitamin D synthesis
- Photothermal interaction: Localized temperature increase causes different effects like coagulation, vaporization, and melting.
Laser-Tissue Interactions
- Transmission: Light passes through tissue without affecting it.
- Reflection: Light bounces off the tissue surface.
- Scattering: Light changes direction but not energy.
- Absorption: Light energy converts to another form within the tissue.
Treatment and Diagnostic By Laser
- Lasers are used in eye surgery (photocoagulation) to shrink or destroy abnormal structures in the retina. .Methods employed include: Xenon lamps Lasers
Photocoagulation
- Uses high power lasers or xenon lamps, to treat retina conditions
- Spot size, energy level required for treatment of retina problems.
- Local anesthesia and short exposure times are preferred depending on the application.
Different Types of Laser Therapy
- Low-Level Laser Therapy (LLLT): Non-invasive, used for musculoskeletal conditions, particularly muscle and connective tissue injuries. Output power is less than 0.5 Watts.
- High-Level Laser Therapy (HLLT): Delivers high-power lasers to penetrate deeply into tissues. Used to treat various conditions, particularly sports injuries. Output power is greater than 0.5 Watts
Advantages of Laser Therapy
- Pain reduction
- Increased ATP levels for faster cell repair
- Reduced inflammation and promotion of beneficial antioxidants.
- Faster wound healing
- Recovery from nerve injuries due to reduced nerve sensitivity.
- Reduced fibrous tissue formation and improvements in vascular activity
- Bone and cartilage formation promotion.
Differences between Lasers & X-rays
- Wavelengths: Lasers have longer wavelengths than X-rays.
- Coherence: Lasers are highly coherent, while X-rays are not.
- Production: Lasers are produced by stimulated emission, while X-rays are produced by high-speed electrons striking a target.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz covers the fundamental concepts of lasers, including their definition, processes, and requirements for beam generation. It explores the characteristics of laser light and its significance in various applications. Test your knowledge on the principles of lasers and their coherent properties.
