Reference
Glossary
Precise definitions of photonics terminology. 721 entries. Filter by name or topic, or jump by letter. Each entry links to the articles and tools where the term is used in context.
721 of 721
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4
A
- Abbe number
- Abbe sine condition
- ABCD matrix (ray transfer matrix)
- Aberrations
- Absorption and emission cross section (σ)
- Absorption coefficient
- Absorption edge
- Acceptance angle
- Acceptance bandwidth
- Achromatic doublet
- Acousto-optic modulator (AOM)
- Active region
- Adaptive optics
- Adiabatic coupler
- Airy disk (Airy pattern)
- Amplified spontaneous emission (ASE)
- Analog optical link (RF photonics, radio over fiber)
- Angle of incidence
- Anti-reflection coating (AR)
- Aperture stop, pupils, chief and marginal rays
- Apodization (apodized gratings and apodizing filters)
- AR waveguide display
- Arc lamp (xenon, mercury)
- Arrayed waveguide grating (AWG)
- Aspheric lens
- Astigmatism
- Auger recombination
- Autocorrelation (pulse measurement)
- Avalanche photodiode (APD)
- Axicon
B
- B-integral (nonlinear phase)
- Back focal length (BFL)
- Balanced detection
- Ball lens
- Band filling (Burstein-Moss shift)
- Bandgap (energy gap, E_g)
- Barium titanate modulator (BTO)
- Beam diameter (1/e², FWHM and D4σ)
- Beam divergence
- Beam dump (beam block)
- Beam expander
- Beam parameter product (BPP)
- Beam profiler
- Beam quality (M²)
- Beam splitter
- Beam steering
- Beam waist (w₀)
- Beat length
- Beer–Lambert law
- Bend loss
- Bias tee
- Birefringence
- Birefringent (Lyot) filter
- Bit error rate (BER)
- Blackbody radiation
- Bolometer
- Boxcar averager (gated integrator)
- Bragg condition (Bragg's law)
- Brewster angle
- Brightness and luminance
- Brillouin scattering
- Broad-area laser diode
- Burn-in
- Burst-mode receiver
C
- C+L band transmission
- Carrier confinement
- Carrier density
- Carrier injection
- Carrier lifetime
- Carrier-envelope offset (CEO)
- Catastrophic optical damage (COD)
- Cavity dumping
- CCD vs CMOS image sensors
- Characteristic matrix method (transfer matrix for thin films)
- Characteristic temperature (T₀)
- Chirped mirror
- Chirped-pulse amplification (CPA)
- Chromatic aberration
- Chromatic dispersion
- Circular polarization
- Cladding modes
- Clear aperture
- Co-packaged optics (CPO)
- CO₂ laser
- Coherence collapse
- Coherence length
- Coherent detection
- Coherent DSP
- Coherent vs incoherent light
- Cold finger
- Collimation
- Color center (NV center, F-center)
- Coma
- Complex refractive index
- Conduction band and valence band
- Confinement factor (Γ)
- Confocal microscopy
- Continuous-wave (CW) vs pulsed lasers
- Core and cladding
- Coupling coefficient (κ)
- Coupling efficiency
- Critical angle
- Critical coupling
- Cross-phase modulation (XPM)
- Cube beamsplitter
- Cutback method
- Cutoff wavelength
- CWDM vs DWDM
- Cylindrical lens
D
- D-factor and MCEF
- Dark count rate (DCR)
- Dark current (I_d)
- de Broglie wavelength
- De-embedding
- Decibel (dB, dBm)
- Delayed self-heterodyne
- Density of states (DOS)
- Depletion region
- Depth of field and depth of focus
- DFB laser array
- Dichroic mirror
- Dichroism
- Die-level test
- Difference-frequency generation (DFG)
- Differential gain
- Differential quantum efficiency
- Differential resistance
- Diffraction
- Diffraction grating
- Diffraction limit
- Diffraction spikes
- Diffuser
- Diffusion length
- Digital micromirror device
- Direct detection
- Direct vs indirect bandgap
- Directional coupler
- Directly modulated laser (DML)
- Dispersion compensation
- Dispersion-shifted fiber (DSF)
- Distortion (optical)
- Distributed acoustic sensing (DAS)
- Distributed Bragg reflector (DBR mirror)
- Distributed Bragg reflector (DBR) laser
- Distributed feedback (DFB) laser
- Distributed temperature sensing (Raman DTS)
- Dither locking (top-of-fringe lock)
- Doppler shift
- Double-clad fiber
- Double-slit experiment
- DPSS laser (diode-pumped solid-state laser)
- Duty cycle
- Dye laser
- Dynamic range
E
- Echelle grating
- Edge coupler
- Edge-emitting laser
- Effective area (A_eff)
- Effective focal length (EFL)
- Effective index (n_eff)
- Effective index method
- Effective mass
- Electrical spectrum analyzer (ESA, RF spectrum analyzer)
- Electro-absorption modulator (EAM)
- Electro-optic effect (Pockels effect)
- Electro-optic modulator (EOM)
- Electroluminescence (EL)
- Electromagnetic spectrum
- Electron-hole pair
- Ellipsometry
- Entangled photons
- Epitaxy (MBE and MOCVD)
- Equalization (FFE, DFE, CTLE)
- Erbium-doped fiber amplifier (EDFA)
- Erbium-doped waveguide amplifier (EDWA)
- Etalon
- Evanescent wave
- Excess noise factor (F)
- Excimer laser
- External cavity laser (ECL)
- External laser source (ELS, ELSFP)
- Extinction ratio (ER)
- Eye diagram
F
- f-number
- Fabry-Perot laser
- Fabry-Perot resonator (FP cavity)
- Facet (laser and waveguide facets)
- Far-field divergence
- Faraday effect
- Faraday rotator
- Fast and slow axis
- FBG sensor
- Fermi level
- Fermi-Dirac distribution
- Few-mode fiber (FMF)
- Fiber array (FAU)
- Fiber attenuation
- Fiber Bragg grating (FBG)
- Fiber cleaving
- Fiber collimator
- Fiber connector types
- Fiber connectors: PC, UPC, APC
- Fiber laser
- Fiber optic splitter
- Fiber patch cord (jumper)
- Fiber polishing
- Fiber-optic gyroscope
- Fiber-optic sensor
- Field curvature
- Field of view (FOV)
- Filling factor
- Finesse
- Finite-difference time-domain (FDTD) method
- First light
- Fixed-pattern noise
- Fizeau interferometer
- Flicker (1/f) noise
- Flip-chip bonded laser
- Fluence
- Fluorescence
- Fluorescence microscopy
- FMCW lidar
- Focal length
- Focal plane
- Forward error correction (FEC)
- Forward voltage (V_f)
- Four-level laser
- Four-wave mixing (FWM)
- Fourier optics
- Franz-Keldysh effect
- Free spectral range (FSR)
- Free-carrier absorption (FCA)
- Free-space optics (FSO)
- Frequency chirp
- Frequency comb
- Fresnel equations
- Fresnel number and Fraunhofer vs Fresnel diffraction
- Fringe visibility (fringe contrast)
- FROG (frequency-resolved optical gating)
- Frustrated total internal reflection
- FTIR spectroscopy
- Full width at half maximum (FWHM)
- Full-well capacity
- Fusion splicing
G
- Gain bandwidth (gain spectrum)
- Gain compression factor (ε)
- Gain medium
- Gain saturation
- Gain switching
- Gain-flattening filter (gain equalization)
- Gallium nitride (GaN)
- Galvo scanner
- Gas laser
- Gaussian beam
- Germanium-on-silicon photodetector
- Gouy phase
- Graded-index fiber
- Grating coupler
- GRIN lens
- Ground state
- Group delay
- Group delay dispersion (GDD)
- Group index (n_g)
- Group velocity
- Group velocity dispersion (GVD)
- Guided mode
H
I
- Ideality factor
- III-V semiconductors
- Image plane
- Impedance matching (50 Ω termination)
- Index contrast
- Index ellipsoid (optical indicatrix)
- Index-matching gel
- Infrared bands (NIR, SWIR, MWIR, LWIR)
- InGaAs photodetector
- Injection locking
- Insertion loss (IL)
- Integrating sphere
- Integration time (exposure time)
- Interband cascade laser (ICL)
- Interference
- Interferometer
- Internal loss (α_i)
- Internal quantum efficiency (η_i)
- Intervalence-band absorption (IVBA)
- Inverse taper
- Irradiance
J
K
L
- Large-mode-area (LMA) fiber
- Laser cooling
- Laser diode (semiconductor laser)
- Laser diode bar
- Laser Doppler vibrometry
- Laser machining
- Laser mirror
- Laser pointer
- Laser threshold
- Lattice matching
- Launch power
- Leaky mode
- Lens
- Lensed fiber
- Lidar
- Light-emitting diode (LED)
- Light-sheet microscopy
- Linear optical sampling (LOS)
- Linear pluggable optics (LPO)
- Lineshape (Lorentzian, Gaussian and Voigt)
- Linewidth
- Linewidth enhancement factor (α)
- Link budget
- Lithium niobate on insulator (LNOI, TFLN)
- LIV curve
- LIV kink
- Local oscillator (LO)
- Lock-in amplifier
- Longitudinal mode spacing
- Longitudinal modes
- LRO (linear receive optics)
M
- Mach-Zehnder modulator (MZM)
- Mach–Zehnder interferometer (MZI)
- Macrobend loss
- Magnification (lateral, angular, longitudinal)
- Malus's law
- Manley-Rowe relations
- Material gain
- MEMS mirror
- Metasurface and metalens
- Micro-transfer printing
- Microbend loss
- Microchannel plate (MCP)
- Microchip laser
- Microcomb (Kerr soliton frequency comb)
- Microring modulator
- Microscope objective
- Mie scattering
- Mirror loss (α_m)
- Modal dispersion
- Modal gain
- Modal noise
- Mode field diameter (MFD)
- Mode hop
- Mode locking
- Mode matching
- Mode mismatch loss
- Mode partition noise (MPN)
- Mode scrambler
- Mode solver
- Modulation bandwidth
- Modulation depth
- Modulation format
- Modulation instability
- Modulation transfer function (MTF)
- Monochromator
- MOPA (master oscillator power amplifier)
- Multi-core fiber (MCF)
- Multi-quantum well (MQW)
- Multimode fiber
- Multimode interference (MMI) coupler
- Multiphoton microscopy
N
- Nd:YAG laser
- Near field and far field
- Near-packaged optics (NPO)
- Network analyzer
- Neuromorphic photonics
- Neutral-density filter
- Noise bandwidth (equivalent noise bandwidth)
- Noise equivalent power (NEP)
- Noise figure (NF)
- Noise floor
- Non-radiative recombination (Shockley-Read-Hall, Auger and surface)
- Non-zero dispersion-shifted fiber (NZ-DSF)
- Nonlinear coefficient
- Nonlinear optics
- Nonlinear susceptibility
- Normal and anomalous dispersion
- Notch filter
- NRZ (Non-Return-to-Zero)
- Numerical aperture (NA)
O
- On-off keying (OOK)
- Optical amplifier
- Optical atomic clock
- Optical axis
- Optical cavity
- Optical circuit switching (OCS)
- Optical circulator
- Optical coherence tomography (OCT)
- Optical computing
- Optical delay line
- Optical density (OD)
- Optical feedback regimes (Tkach–Chraplyvy)
- Optical fiber
- Optical filter
- Optical frequency domain reflectometry (OFDR)
- Optical gain
- Optical hybrid (90° hybrid)
- Optical I/O (chiplet optics)
- Optical isolator
- Optical parametric amplifier (OPA)
- Optical parametric oscillator (OPO)
- Optical path length
- Optical phase shifter
- Optical phase-locked loop (OPLL)
- Optical phased array (OPA)
- Optical power meter
- Optical pumping
- Optical return loss
- Optical signal-to-noise ratio (OSNR)
- Optical soliton
- Optical spectrum analyzer (OSA)
- Optical time-domain reflectometry (OTDR)
- Optical transceiver / transponder
- Optical tweezers
- Optical window
- Output coupler
P
- P-n junction
- PAM4
- Paraxial approximation
- Passive optical network (PON)
- Peak power
- Pellicle beamsplitter
- Permittivity and dielectric constant
- Petermann factor
- Phase matching
- Phase noise and frequency noise
- Phase velocity
- Phonon
- Phosphor
- Photoacoustics
- Photoconductive detector (photoconductive gain)
- Photodiode
- Photodiode array
- Photoelastic effect (stress-optic effect)
- Photoelectric effect (work function)
- Photoluminescence (PL)
- Photomultiplier tube (PMT)
- Photon
- Photon counting
- Photon energy
- Photon flux
- Photon lifetime (cavity lifetime)
- Photon statistics
- Photon transfer curve
- Photon-number-resolving detector
- Photonic crystal
- Photonic crystal fiber (PCF)
- Photonic integrated circuit (PIC)
- Photonic quantum computing
- Photonic tensor core
- Photonic wire bonding
- Photonic-crystal surface-emitting laser (PCSEL)
- Picosecond laser
- Pigtailing
- PIN photodiode
- Plane wave
- Plasma dispersion effect (Soref-Bennett relations)
- Pluggable optics
- Pockels cell
- Pockels effect (linear electro-optic effect)
- Point spread function (PSF)
- Polarization
- Polarization controller
- Polarization extinction ratio (PER)
- Polarization mode dispersion (PMD)
- Polarization splitter-rotator (PSR)
- Polarization states
- Polarization-dependent loss (PDL)
- Polarization-maintaining (PM) fiber
- Polarized light microscopy
- Polarizer
- Polymer optical fiber
- Population inversion
- Pound-Drever-Hall locking (PDH)
- Power density
- Power penalty
- Power spectral density (PSD)
- Poynting vector
- Principal planes
- Prism
- Prism coupler
- Probabilistic constellation shaping
- Probe station
- Process design kit (PDK)
- Propagation constant (β)
- Propagation loss
- Pseudo-random binary sequence (PRBS)
- Pulse compressor
- Pulse duration
- Pulse energy
- Pulse picker
- Pump combiner (tapered fiber bundle)
- Pump-probe spectroscopy
- Purcell effect
- Pyroelectric detector
Q
- Q-switching
- QAM (Quadrature Amplitude Modulation)
- Quality factor (Q)
- Quantum cascade laser (QCL)
- Quantum defect
- Quantum dot laser
- Quantum efficiency
- Quantum key distribution (QKD)
- Quantum photonic integrated circuit (QPIC)
- Quantum well
- Quantum-confined Stark effect (QCSE)
- Quasi-Fermi level
- Quasi-phase matching (QPM)
R
- Radiance
- Radiative recombination
- Radiometry vs photometry
- Raman amplifier
- Raman scattering
- Raman spectroscopy
- Rare-earth ions (as laser and amplifier dopants)
- Rate equations
- Ray tracing
- Rayleigh criterion
- Rayleigh range
- Rayleigh scattering
- RC time constant (RC-limited bandwidth)
- Read noise
- Receiver sensitivity
- Reflection
- Refraction
- Refractive index (n)
- Regenerative amplifier
- Relative intensity noise (RIN)
- Relaxation oscillations
- Repetition rate
- Resolution bandwidth
- Resonant saturable absorber mirror (RSAM)
- Resonator stability
- Responsivity (R)
- Retardance
- Retimer (clock and data recovery)
- Retroreflector
- Reverse bias
- Ridge-waveguide laser
- Ring resonator
- Rise time (10–90%)
- ROADM and wavelength-selective switch (WSS)
S
- s- and p-polarization
- Sampling oscilloscope
- Saturable absorber
- Saturation power (P_sat)
- Scanning Fabry-Perot interferometer
- Scattering
- Schawlow–Townes linewidth
- Second-harmonic generation (SHG)
- Self-focusing
- Self-injection locking
- Self-phase modulation (SPM)
- Sellmeier equation
- Semiconductor optical amplifier (SOA)
- Semiconductor saturable absorber mirror (SESAM)
- Separate-confinement heterostructure (SCH, GRINSCH)
- SerDes (serializer and deserializer)
- Series resistance
- Shack-Hartmann wavefront sensor
- Shot noise
- Shunt resistance
- Side-mode suppression ratio (SMSR)
- Sidewall roughness
- Signal-to-noise ratio (SNR)
- Silicon nitride photonics
- Silicon photomultiplier (SiPM)
- Silicon-on-insulator (SOI)
- Single-mode fiber
- Single-mode vs multimode fiber
- Single-photon avalanche diode (SPAD)
- Single-photon source
- Single-slit diffraction
- Slab waveguide
- Slope efficiency
- Small-signal gain
- Snell's law
- Solar cell
- Solid angle
- Solid-state laser
- Source-measure unit (SMU)
- Space-division multiplexing (SDM)
- Spatial coherence
- Spatial filter
- Spatial hole burning
- Spatial light modulator
- Specific detectivity (D*)
- Speckle
- Spectral efficiency
- Spectral hole burning
- Spectrometer
- Speed of light
- Speed of light in fiber
- Spherical aberration
- Spontaneous emission
- Spontaneous emission factor (β)
- Spontaneous parametric down-conversion (SPDC)
- Spot-size converter (SSC)
- Squeezed light
- Standing wave
- Step-index fiber
- Stimulated Brillouin scattering (SBS)
- Stimulated emission
- Stimulated Raman scattering (SRS)
- Stokes parameters
- Stop band
- Strained quantum well
- Stray light
- Streak camera
- Strehl ratio
- Strip vs rib waveguide
- Submarine cable
- Submount
- Substrate leakage
- Sum-frequency generation (SFG)
- Superconducting nanowire single-photon detector (SNSPD)
- Supercontinuum generation
- Superluminescent diode (SLD)
- Surface plasmon (polariton)
- SWIR camera
- Symbol rate
T
- T2* (dephasing time)
- Tapered amplifier
- TDECQ
- TE and TM polarization
- Telecom wavelength bands (O-band, C-band, L-band)
- Telescope (refracting, reflecting, Cassegrain)
- TEM00 mode
- Temporal coherence
- Terahertz generation
- Thermal detector
- Thermal lensing
- Thermal noise
- Thermal resistance
- Thermal rollover
- Thermistor (NTC)
- Thermo-optic phase shifter
- Thermoelectric cooler (TEC)
- Thermopile
- Thin-disk laser
- Thin-film filter (TFF)
- Thin-film interference
- Third-harmonic generation (THG)
- Threshold condition
- Threshold current (laser diode)
- Threshold current density (J_th)
- Thulium fiber laser
- Ti:sapphire laser
- Time of flight (ToF)
- Time-bandwidth product
- Time-bin encoding (time-bin qubits)
- Time-correlated single-photon counting (TCSPC)
- Timing jitter
- Total internal reflection (TIR)
- Tracking error
- Transimpedance amplifier (TIA)
- Transit time
- Transmittance
- Transparency current (I_tr)
- Transverse modes
- Transverse wave
- Traveling-wave electrode (velocity matching)
- Tunable diode laser absorption spectroscopy (TDLAS)
- Tunable laser
- Two-photon absorption (TPA)