Michael Bukshtab

Applied Photometry, Radiometry, and Measurements of Optical Losses

Sprin ger

Contents

Part I Applied Photometry and Radiometry

1 Radiometric and Photometric Quantities and Notions 3 1.1 Physical Sense of Radiometric Conception 3

1.1.1 Statistical Field of Optical Radiation 3 1.1.2 Propagation of Light Waves 4 1.1.3 Intensity of Radiation and Light Rays 6

1.2 Parameters of Optical Radiation 9 1.2.1 Radiometric Quantities and Units 9 1.2.2 Parameters of Optical Radiation 12 1.2.3 Invariable Parameters of a Light Tube 15 1.2.4 Flux and Radiance of Optical Radiation 18 1.2.5 Intensity and Emittance of a Light Beam 20 1.2.6 Irradiance and the Inverse-Square and Cosine Law 24

1.3 Interactions of Radiation with Material Objects 27 1.3.1 Factors and Coefficients of Attenuation 27 1.3.2 Localized Optical Properties 33 1.3.3 Multiple Optical Elements 36 1.3.4 Diffuse Irradiation 40

2 Methods of Photometric and Radiometric Measurements 49 2.1 Evaluation of Power and Energy Extents of Optical Radiation 49

2.1.1 Methods of Optical Flux and Energy Measurements 49 2.1.2 Measurement of Surface Density of Light 53 2.1.3 Absolute Flux Measurement Via an

Integrating Sphere 55 2.1.4 Spherical Density of Radiation 56 2.1.5 Measurement of Angular Density of Radiation 59 2.1.6 Radiance and Luminance Measurements 60

2.2 Analysis of Attenuation Factors 62 2.2.1 Measurements in Transmitted Light 63

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xvi Contents

2.2.2 Measurements of Reflectance 66 2.2.3 Directional Scattering Measurements 73

2.3 Measurements of Color Coordinates and Indices 76 2.4 Photometry of Integrating Spheres 92

2.4.1 Uniformly Scattering Spheres 92 2.4.2 Relative Measurements 95 2.4.3 Samples Performing as Nonuniform Diffusers 99 2.4.4 Absolute Measurements in an Integrating Sphere 99 2.4.5 Baffling Method 101 2.4.6 Efficiency Approach 102 2.4.7 Viewing Method 103 2.4.8 Reduction of Systematic Errors of Absolute

Measurements 104 2.4.9 Spheres of Nonisotropic Diffusers 108 2.4.10 Fully Isotropic Irradiation of Integrating Sphere 112 2.4.11 Essentials of Diffuse Transmittance Measurements 114 2.4.12 Separation of Direct and Diffuse Transmittance 116 2.4.13 Coupling of Integrating Spheres 118 2.4.14 Integrating Spheres for Isotropic Irradiation 121

3 Radiometry of Partially Coherent Radiation 129 3.1 Coherence and Radiative Transfer 129

3.1.1 Observability and Statistical Properties of Radiation 129 3.1.2 Planar Sources of Incoherent and Coherent Light 135 3.1.3 Quasi-Homogeneous Partially Coherent

Planar Sources 137 3.1.4 Propagation of Coherence and Observation

of Polychromatic Radiation 141 3.1.5 Summary 144

3.2 Laser and Pulsed Light 144 3.2.1 Propagation Extents of Laser Radiation 144 3.2.2 Applicability of Lasers for Various Optical

Measurements 147 3.2.3 Optical Radiation as a Pulse Train 151 3.2.4 Measurements in Pulsed Radiation 154

3.3 Interference Phenomena and Optical Measurements 159 3.3.1 Fringe Visibility of Interference Patterns in

Transmitted and Reflected Light 159 3.3.2 Reductions of Interference Noise 163 3.3.3 Interference Effects Induced by Birefringence 170 3.3.4 Stabilization of Radiation Emission 180 3.3.5 Polarization Measurements 184

3.4 Diffraction Corrections and Gratings in Radiometry and Photometry 187

Contents xvii

3.4.1 Maxima-Shifting Anomaly for Step-Function Diffraction Grating in Reflected Light 192

3.4.2 Diffraction Gratings as Spectral and Color Filters 214

4 Photometers and Radiometers 217 4.1 Optical Design and Absolute Calibration of Radiometers 217

4.1.1 Spectrally Unselective Systems 217 4.1.2 Diffuse Attenuators 222 4.1.3 Radiometric and Photometric Energy and

Power Scales 227 4.1.4 Absolute Calibration of Photoelectric Radiometers 229 4.1.5 Detector-Based Spectroradiometric and

Photometric Scales 231 4.1.6 Optical Elements of Radiometric and

Photometric Standards 235 4.1.7 Radiometric and Photometric Scales for

Spectral Irradiance and Luminous Intensity 238 4.2 Attenuation and Color Photometers and Spectrophotometers 240

4.2.1 Measurements of Direct Transmittance and Specular Reflectance 240

4.2.2 Polychromatic and Spectrophotometric Systems 243 4.2.3 Reference Transmission Spectrophotometers 245 4.2.4 Specialty Spectrophotometers 248 4.2.5 Systems of Multiple-Beam Interactions 250 4.2.6 Measurements at Intensive Irradiation 252 4.2.7 Studies of Integrated Scattering 253 4.2.8 Specialty Applications of Integrating Spheres

for Optical Calibrations and Measurements 261 4.2.9 Color-Coordinate Measurements 264

4.3 Photometric Accuracy and Verification of Linearity 268 4.3.1 Measurements with Fixed Attenuation 269 4.3.2 Dual-Aperture and Superposition Methods 274 4.3.3 Pulsed Measurements 276 4.3.4 Arrangements for Light Addition Studies 279

Part II Measurements of Optical Losses

5 Conventional Loss-Measurement Techniques 289 5.1 Internal Transmittance and Attenuation Coefficient 289 5.2 Specular Reflectance 299 5.3 Scattering Factor 309

6 Systems of Multiple Reflections 321 6.1 Flat-Mirror and Prism Reflector Cells 321 6.2 Multipass Cavities 328

6.2.1 Long-Path Matrix Cells 332

Contents

6.3 Mirror Waveguides 342 6.4 Multiplication of Raman Scattering 348 6.5 Interference-Fringe Reduction in Multipass

and Derivative Spectroscopy 359 Laser Spectroscopy 367 7.1 Active Intracavity Measurements 367 7.2 Comparison of Intracavity Methods 373 7.3 Intracavity and Ringdown Spectroscopy 378

7.3.1 Sensitivity Limitations of Intracavity Laser Spectroscopy 382 7.3.2 Cavity Ringdown Spectroscopy 384 7.3.3 Multimode Versus Single-Mode Studies 392 7.3.4 Continuous-Wave Ringdown Spectrometers 396 7.3.5 Cavity-Enhanced Broadband Spectroscopy 398

Measurements in Passive Resonators 401 8.1 Pulse-Separation Techniques 401 8.2 Interferometric Analysis 409

8.2.1 Elimination of Interference 414 8.3 Resonant Phase-Shift and Decay-Time Studies 417

8.3.1 Interference Safeguards 420 8.3.2 Decay-Time Measurements 423

8.4 Quality-Factor Transfer Method and Asymmetric-Cavity Measurements 431 8.4.1 Measurements in Tuning Resonators 436 8.4.2 Quality-Factor Transition Between Two

Resonator Eigenstates 438 8.4.3 Nonresonant, Off-Axis Techniques 441 8.4.4 Resonant Asymmetric-Cavity Techniques 443

8.5 Evaluation of Loss Dichroism and Phase Dispersion 447 8.5.1 Recognition of Phase Dispersion 450 8.5.2 In Situ Laser-Based Measurements 453 8.5.3 Spectrophotometric Study of Phase Dispersion 455 8.5.4 Colorimetric Approach to Phase Recognition 461 8.5.5 Spatial-Spectral Interferometry 463

Determination of Absorption Losses 469 9.1 Laser Calorimetry 469

9.1.1 Local Absorptance 479 9.2 Thermal-Lensing, Photothermal, and Photoacoustic Techniques .. 482

9.2.1 Thermal Lensing 483 9.2.2 Photothermal Deflection 489 9.2.3 Photothermal Interferometry 495 9.2.4 Photoacoustic Spectroscopy 504 9.2.5 In Situ and Remote Photoacoustic Spectroscopies 508 9.2.6 Trace-Gas Photoacoustic Analysis 511

Contents xix

9.3 Emissive Spectroscopy 517 9.4 Integrating Spheres as Multiple-Reflection Cavities 521

9.4.1 Integrating-Cavity Absorption Measurements 521 9.4.2 Integrating Spheres as Absorption Cells for

Gaseous Substances 531

10 Direct Attenuation Measurements 537 10.1 Differential, Ratio, and Single-Channel Systems 537 10.2 Derivative Spectroscopy 546 10.3 Wavelength Tuning and Balanced Detection 555

10.3.1 Tunable Diode Systems 556 10.3.2 Balanced Detection 563

10.4 Separation of Bulk and Surface Losses 567 10.4.1 Distinction of Surface Losses 568 10.4.2 Resolving Internal Properties 571

10.5 Reflection Spectrophotometry 576 10.5.1 Reflected-Light Measurements 584 10.5.2 Sensitivity Comparison 586

11 Propagation Losses in Fibers and Waveguides 589 11.1 Measurements of Internal Optical Attenuation

for Guided Light 589 11.1.1 Integrated Waveguides 594 11.1.2 Absorption and Scattering Losses 597 11.1.3 Analysis of Scattering Losses 601 11.1.4 Polarization Dependent Losses 605

11.2 Analysis of Return Losses via Backscattered Radiation 610 11.3 Partition of Distributed Losses and Attenuation Factors

in Reflected Light 617 11.4 Interference Noise and Crosstalk in Fiber Transmission Systems . 629

11.4.1 Crosstalk and Systems with Multiple Interferers 641

References 653

Index 691