15 FIELD GUIDES · 2 WORKED EXAMPLES
Where does the light go?
Follow optical power, direction, polarization and loss to understand how light interacts with materials and transfers momentum.
Light & optical momentum
Start with the question closest to your experiment. Each guide separates the mechanism, an illustrative example, and the evidence needed for the next decision.
Photon momentum and radiation pressure
Compute optical force from the change in momentum flux, keeping absorption, reflection, transmission, beam direction, and the chosen system boundary explicit.
Read the guide ↗FIELD GUIDEReflectance, absorptance, and transmittance
Keep power fractions distinct from field amplitudes and logarithmic absorbance, and collect scattered light before inferring absorption from a power deficit.
Read the guide ↗FIELD GUIDERadiation pressure at oblique incidence
Distinguish intercepted beam power from intensity per surface area when projecting optical momentum onto a tilted mirror and its sensitive force axis.
Read the guide ↗FIELD GUIDEDiffraction orders carry separate momentum
A grating redistributes light among allowed directions; calculate force from the power in each propagating order instead of treating diffraction as a loss.
Read the guide ↗FIELD GUIDEWhat an integrating sphere collects
An integrating sphere helps collect diffuse optical power, but ports, coating response, sample substitution, and detector calibration still shape the result.
Read the guide ↗FIELD GUIDECalibrate the power that reaches the experiment
Optical power at a source is not necessarily power at the sample; account for wavelength response, beam collection, timing, attenuation, and detector linearity.
Read the guide ↗FIELD GUIDEPolarization changes interaction, not just appearance
Describe the electric-field state and optical basis before comparing polarization-dependent reflection, absorption, diffraction, or force measurements.
Read the guide ↗FIELD GUIDECoherence vs scattering
Coherence concerns phase correlations, while scattering redistributes optical fields; distinguish lost interference contrast from lost power or momentum.
Read the guide ↗FIELD GUIDEStored cavity energy and force bookkeeping
A resonator can store energy and increase internal optical loads while the complete assembly still obeys external energy and momentum balance.
Read the guide ↗FIELD GUIDEFinesse vs quality factor
Finesse compares linewidth with mode spacing, while optical Q compares linewidth with carrier frequency; use the definition that answers the design question.
Read the guide ↗FIELD GUIDEPhase index, group index, and dispersion
Use phase index for wave phase and group index for narrowband envelope delay; dispersion can reshape pulses and change resonator mode spacing.
Read the guide ↗FIELD GUIDEHow gating changes graphene optics
Gating changes carrier occupation and optical conductivity in graphene; separate the optical modulation from electrode forces and temperature changes.
Read the guide ↗FIELD GUIDEOptical loss becomes heat only through absorption
Separate absorption from scattering and outcoupling, then connect absorbed power to temperature using a thermal model of the illuminated structure.
Read the guide ↗FIELD GUIDEEvanescent fields and near-field momentum
An evanescent field decays away from an interface while remaining able to exchange energy and momentum with nearby matter under the right coupling conditions.
Read the guide ↗FIELD GUIDEOptical torque follows angular momentum transfer
Calculate torque from changes in optical angular momentum, separating polarization spin, spatial structure, and ordinary force acting through a lever arm.
Read the guide ↗PUT THE IDEAS TO WORK
Follow the calculation.
Two outgoing beams require a vector momentum balance
Calculate recoil from the directions of all beams, not their total power alone.
Read the guide ↗WORKED EXAMPLEA small absorbed fraction can dominate a thermal signal
Compare optical momentum with the temperature rise caused by absorption.
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