CONTENTS SEARCH HANDBOOK   PREFACE TO THE SIXTH EDITION 11   1. SPECTROSCOPY AND GRATINGS 13    1.0. INTRODUCTION 13    1.1. THE DIFFRACTION GRATING 14    1.2. A BRIEF HISTORY OF GRATING DEVELOPMENT 15    1.3. HISTORY OF THE NEWPORT GRATINGS OPERATION 16    1.4. DIFFRACTION GRATINGS FROM NEWPORT 17    2. THE PHYSICS OF DIFFRACTION GRATINGS 19    2.1. THE GRATING EQUATION 19    2.2. DIFFRACTION ORDERS 24    2.2.1. Existence of diffraction orders 24    2.2.2. Overlapping of diffracted spectra 25    2.3. DISPERSION 27    2.3.1. Angular dispersion 27    2.3.2. Linear dispersion 28    2.4. RESOLVING POWER, SPECTRAL RESOLUTION, AND BANDPASS 30    2.4.1. Resolving power 30    2.4.2. Spectral resolution 32    2.4.3. Bandpass 33    2.4.4. Resolving power vs. resolution 33    2.5. FOCAL LENGTH AND f/NUMBER 34    2.6. ANAMORPHIC MAGNIFICATION 36    2.7. FREE SPECTRAL RANGE 37    2.8. ENERGY DISTRIBUTION (GRATING EFFICIENCY) 37    2.9. SCATTERED AND STRAY LIGHT 40    2.10. SIGNAL-TO-NOISE RATIO (SNR) 40    3. RULED GRATINGS 43    3.0. INTRODUCTION 43    3.1. RULING ENGINES 43    3.1.1. The Michelson engine 44    3.1.2. The Mann engine 44    3.1.3. The MIT 'B' engine 45    3.2. THE RULING PROCESS 46    3.3. VARIED LINE-SPACE (VLS) GRATINGS 47    4. HOLOGRAPHIC GRATINGS 49    4.0. INTRODUCTION 49    4.1. PRINCIPLE OF MANUFACTURE 50    4.1.1. Formation of an interference pattern 50    4.1.2. Formation of the grooves 51    4.2. CLASSIFICATION OF HOLOGRAPHIC GRATINGS 52    4.2.1. Single-beam interference 52    4.2.2. Double-beam interference 53    4.3. THE RECORDING PROCESS 55    4.4. DIFFERENCES BETWEEN RULED AND HOLOGRAPHIC GRATINGS 56    4.4.1. Differences in grating efficiency 56    4.4.2. Differences in scattered light 57    4.4.3. Differences and limitations in the groove profile 57    4.4.4. Limitations in obtainable groove frequencies 59    4.4.5. Differences in the groove patterns 59    4.4.6. Differences in the substrate shapes 60    4.4.7. Differences in the size of the master substrate 60    4.4.8. Differences in generation time for master gratings 61    5. REPLICATED GRATINGS 63    5.0. INTRODUCTION 63    5.1. THE REPLICATION PROCESS 63    5.2. REPLICA GRATINGS VS. MASTER GRATINGS 68    5.3. STABILITY OF REPLICATED GRATINGS 70    6. PLANE GRATINGS AND THEIR MOUNTS 75    6.1. GRATING MOUNT TERMINOLOGY 75    6.2. PLANE GRATING MONOCHROMATOR MOUNTS 75    6.2.1. The Czerny-Turner monochromator 76    6.2.2. The Ebert-Fastie monochromator 77    6.2.3. The Monk-Gillieson monochromator 78    6.2.4. The Littrow monochromator 79    6.2.5. Double & triple monochromators 80    6.2.6. The constant-scan monochromator 82    6.3. PLANE GRATING SPECTROGRAPH MOUNTS 83    7. CONCAVE GRATINGS AND THEIR MOUNTS 85    7.0. INTRODUCTION 85    7.1. CLASSIFICATION OF THE GRATING TYPES 85    7.1.1. Groove patterns 86    7.1.2. Substrate (blank) shapes 87    7.2. CLASSICAL CONCAVE GRATING IMAGING 88    7.3. NONCLASSICAL CONCAVE GRATING IMAGING 95    7.4. REDUCTION OF ABERRATIONS 98    7.5. CONCAVE GRATING MOUNTS 101    7.5.1. The Rowland circle spectrograph 101    7.5.2. The Wadsworth spectrograph 103    7.5.3. Flat-field spectrographs 103    7.5.4. Imaging spectrographs and monochromators 105    7.5.5. Constant-deviation monochromators 106    8. IMAGING PROPERTIES OF GRATING SYSTEMS 109    8.1. CHARACTERIZATION OF IMAGING QUALITY 109    8.1.1. Geometric raytracing & spot diagrams 109    8.1.2. Linespread calculations 111    8.2. INSTRUMENTAL IMAGING 112    8.2.1. Magnification of the entrance aperture 112    8.2.2. Effects of the entrance aperture dimensions 115    8.2.3. Effects of the exit aperture dimensions 117    8.3. INSTRUMENTAL BANDPASS 121    9. EFFICIENCY CHARACTERISTICS OF DIFFRACTION GRATINGS 123    9.0. INTRODUCTION 123    9.1. GRATING EFFICIENCY AND GROOVE SHAPE 126    9.2. EFFICIENCY CHARACTERISTICS FOR TRIANGULAR-GROOVE GRATINGS 128    9.3. EFFICIENCY CHARACTERISTICS FOR SINUSOIDAL-GROOVE GRATINGS 134    9.4. THE EFFECTS OF FINITE CONDUCTIVITY 138    9.5. DISTRIBUTION OF ENERGY BY DIFFRACTION ORDER 139    9.6. USEFUL WAVELENGTH RANGE 142    9.7. BLAZING OF RULED TRANSMISSION GRATINGS 142    9.8. BLAZING OF HOLOGRAPHIC REFLECTION GRATINGS 143    9.9. OVERCOATING OF REFLECTION GRATINGS 143    9.11. THE RECIPROCITY THEOREM 145    9.12. CONSERVATION OF ENERGY 146    9.13. GRATING ANOMALIES 147    9.13.1. Rayleigh anomalies 148    9.13.2. Resonance anomalies 148    9.14. GRATING EFFICIENCY CALCULATIONS 150    10. STRAY LIGHT CHARACTERISTICS OF GRATINGS AND GRATING SYSTEMS 153    10.0. INTRODUCTION 153    10.1. GRATING SCATTER 153    10.1.1. Surface irregularities in the grating coating 155    10.1.2. Dust, scratches & pinholes on the surface of the grating 155    10.1.3. Irregularities in the position of the grooves 155    10.1.4. Irregularities in the depth of the grooves 156    10.1.5. Spurious fringe patterns due to the recording system 156    10.1.6. The perfect grating 157    10.2. INSTRUMENTAL STRAY LIGHT 158    10.2.1. Grating scatter 158    10.2.2. Other diffraction orders from the grating 158    10.2.3. Overfilling optical surfaces 159    10.2.4. Direct reflections from other surfaces 159    10.2.5. Optical effects due to the sample or sample cell 161    10.2.6. Thermal emission 161    10.3. ANALYSIS OF OPTICAL RAY PATHS IN A GRATING-BASED INSTRUMENT 161    10.4. DESIGN CONSIDERATIONS FOR REDUCING STRAY LIGHT 164    11. TESTING AND CHARACTERIZING DIFFRACTION GRATINGS 169    11.1. THE MEASUREMENT OF SPECTRAL DEFECTS 169    11.1.1. Rowland ghosts 170    11.1.2. Lyman ghosts 172    11.1.3. Satellites 172    11.2. THE MEASUREMENT OF GRATING EFFICIENCY 174    11.3. THE MEASUREMENT OF DIFFRACTED WAVEFRONT QUALITY 175    11.3.1. The Foucault knife-edge test 175    11.3.2. Direct wavefront testing 177    11.4. THE MEASUREMENT OF RESOLVING POWER 179    11.5. THE MEASUREMENT OF SCATTERED LIGHT 181    11.6. THE MEASUREMENT OF INSTRUMENTAL STRAY LIGHT 183    11.6.1. The use of cut-off filters 183    11.6.2. The use of monochromatic light 185    11.6.3. Signal-to-noise and errors in absorbance readings 186    12. SELECTION OF DISPERSING SYSTEMS 187    12.1. REFLECTION GRATING SYSTEMS 187    12.1.1. Plane reflection grating systems 187    12.1.2. Concave reflection grating systems 188    12.2. TRANSMISSION GRATING SYSTEMS 189    12.3. GRATING PRISMS (GRISMS) 191    12.4. GRAZING INCIDENCE SYSTEMS 193    12.5. ECHELLES 193    13. APPLICATIONS OF DIFFRACTION GRATINGS 199    13.1. GRATINGS FOR INSTRUMENTAL ANALYSIS 199    13.1.1. Atomic and molecular spectroscopy 199    13.1.2. Fluorescence spectroscopy 201    13.1.3. Colorimetry 201    13.1.4. Raman spectroscopy 202    13.2. GRATINGS IN LASER SYSTEMS 202    13.2.1. Laser tuning 203    13.2.2. Pulse stretching and compression 205    13.3. GRATINGS IN ASTRONOMICAL APPLICATIONS 206    13.3.1. Ground-based astronomy 206    13.3.2. Space-borne astronomy 210    13.4. GRATINGS IN SYNCHROTRON RADIATION BEAMLINES 210    13.5. SPECIAL USES FOR GRATINGS 210    13.5.1. Gratings as filters 211    13.5.2. Gratings in fiber-optic telecommunications 211    13.5.3. Gratings as beam splitters 213    13.5.4. Gratings as optical couplers 214    13.5.5. Gratings in metrological applications 214    14. ADVICE TO GRATING USERS 215    14.1. CHOOSING A SPECIFIC GRATING 215    14.2. APPEARANCE 216    14.2.1. Ruled gratings 216    14.2.2. Holographic gratings 217    14.3. GRATING MOUNTING 217    14.4. GRATING SIZE 217    14.5. SUBSTRATE MATERIAL 218    14.6. GRATING COATINGS 218    15. HANDLING GRATINGS 219    15.1. THE GRATING SURFACE 219    15.2. PROTECTIVE COATINGS 219    15.3. GRATING COSMETICS AND PERFORMANCE 220    15.4. UNDOING DAMAGE TO THE GRATING SURFACE 221    15.5. GUIDELINES FOR HANDLING GRATINGS 222    16. GUIDELINES FOR SPECIFYING GRATINGS 223    16.1. REQUIRED SPECIFICATIONS 223    16.2. SUPPLEMENTAL SPECIFICATIONS 227    16.3. ADDITIONAL REQUIRED SPECIFICATIONS FOR CONCAVE ABERRATION-REDUCED GRATINGS 228  APPENDIX A.  SOURCES OF ERROR IN MONOCHROMATOR- MODE EFFICIENCY MEASUREMENTS OF PLANE DIFFRACTION GRATINGS 233    A.0. INTRODUCTION 233    A.1. OPTICAL SOURCES OF ERROR 235    A.1.1. Wavelength error 235   A.1.2. Fluctuation of the light source intensity 237   A.1.3. Bandpass 237   A.1.4. Superposition of diffracted orders 238   A.1.5. Degradation of the reference mirror 239   A.1.6. Collimation 240   A.1.7. Stray light or "optical noise" 240   A.1.8. Polarization 241   A.1.9. Unequal path length 242   A.2. MECHANICAL SOURCES OF ERROR 242    A.2.1. Alignment of incident beam to grating rotation axis 242   A.2.2. Alignment of grating surface to grating rotation axis 243   A.2.3. Orientation of the grating grooves (tilt adjustment) 243   A.2.4. Orientation of the grating surface (tip adjustment) 243   A.2.5. Grating movement 244   A.3. ELECTRICAL SOURCES OF ERROR 244    A.3.1. Detector linearity 244   A.3.2. Changes in detector sensitivity 245   A.3.3. Sensitivity variation across detector surface 246   A.3.4. Electronic Noise 246   A.4. ENVIRONMENTAL FACTORS 246    A.4.1. Temperature 246   A.4.2. Humidity 247   A.4.3. Vibration 247   A.5. SUMMARY 248    APPENDIX B.  LIE ABERRATION THEORY FOR GRATING SYSTEMS 249   FURTHER READING 253   GRATING PUBLICATIONS BY NEWPORT CORPORATION PERSONNEL 255   back to top