Lasers

10 Pages

English

Undergraduate

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Laser Principles

1. Light, Photons, and Atomic Energy Levels

2. Absorption and Spontaneous Emission

3. Stimulated Emission and Optical Amplification

4. Creating Population Inversion

5. Optical Resonators and Feedback

Laser Systems and Applications

6. Gain Media and Optical Pumping

7. Gas, Solid-State, and Semiconductor Lasers

8. Understanding Laser Beam Properties

9. Lasers Across Science, Technology, and Healthcare

10. Laser Safety and Engineering Constraints

1. Light, Photons, and Atomic Energy Levels

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Why do different laser materials produce different colors or wavelengths?

Does a photon have mass?

Photon:

Energy level:

Planck’s constant:

Wavelength:

Photon:

Energy level:

Planck’s constant:

Wavelength:

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2. Absorption and Spontaneous Emission

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Why is spontaneous emission not laser light by itself?

Can absorption occur for any color of incident light?

Absorption:

Spontaneous emission:

Excited-state lifetime:

Incoherent light:

Absorption:

Spontaneous emission:

Excited-state lifetime:

Incoherent light:

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3. Stimulated Emission and Optical Amplification

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Are the original and stimulated photons identical in every possible sense?

Why does stimulated emission preserve phase?

Stimulated emission:

Coherence:

Optical gain:

Gain coefficient:

Stimulated emission:

Coherence:

Optical gain:

Gain coefficient:

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4. Creating Population Inversion

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Why is a two-level system usually unsuitable for a continuous laser?

Why are four-level lasers often easier to operate than three-level lasers?

Population inversion:

Pumping:

Metastable state:

Laser threshold:

Population inversion:

Pumping:

Metastable state:

Laser threshold:

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5. Optical Resonators and Feedback

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Why not make both cavity mirrors perfectly reflecting?

What happens if the cavity length changes slightly?

Optical resonator:

Output coupler:

Longitudinal mode:

Round-trip condition:

Optical resonator:

Output coupler:

Longitudinal mode:

Round-trip condition:

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6. Gain Media and Optical Pumping

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Why does ordinary heating not usually produce laser light?

Why is one cavity mirror partly transparent?

Gain medium:

Population inversion:

Threshold gain:

Optical resonator:

Gain medium:

Population inversion:

Threshold gain:

Optical resonator:

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7. Gas, Solid-State, and Semiconductor Lasers

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Why are diode lasers widely used despite often having lower beam quality than some solid-state lasers?

Can a solid-state laser emit visible light if Nd:YAG emits infrared?

He–Ne laser:

Nd:YAG laser:

CO₂ laser:

Semiconductor laser:

He–Ne laser:

Nd:YAG laser:

CO₂ laser:

Semiconductor laser:

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8. Understanding Laser Beam Properties

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Does coherent light always have a single wavelength?

Why does a laser beam still spread as it travels?

Coherence length:

Beam divergence:

Gaussian beam:

Monochromaticity:

Coherence length:

Beam divergence:

Gaussian beam:

Monochromaticity:

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9. Lasers Across Science, Technology, and Healthcare

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Why are infrared wavelengths common in fiber-optic communication?

Why can pulsed lasers machine materials more precisely than continuous beams?

Spectroscopy:

Ablation:

Optical fiber window:

Fluence:

Spectroscopy:

Ablation:

Optical fiber window:

Fluence:

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10. Laser Safety and Engineering Constraints

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Why are ordinary sunglasses not appropriate laser safety eyewear?

Is a diffuse reflection always safe to view?

Laser class:

Nominal ocular hazard distance:

Thermal lensing:

Specular reflection:

Laser class:

Nominal ocular hazard distance:

Thermal lensing:

Specular reflection:

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