Technical notes and assessments. Every claim comes with its primary source.
From the photoelectric effect to antibunching: the three criteria that force light to be treated as a quantum field — single-photon level, non-classical correlations (g(2)(0) < 1), and vacuum fluctuations — plus the HBT measurement method.
Follow a consistent phase-encoded decoy-state BB84 example from two-bin states and SPAD events to authenticated processing; distinguish detection, QBER and finite-key security.
See how clock-aligned waveforms form an eye, compare noise, jitter and ISI on common scales, and read eye height/width with stated statistical rules. Eye appearance alone does not establish BER.
Four figures connect specialty-fiber structures to PM alignment, double-clad pumping and effective mode area. Distinguish physical core size, MFD, pump-launch channels and M², and read named-product specs with their test conditions.
How relative grating displacement becomes quadrature signals and a fine output step: connected transmission optics, grating overlap, sine/cosine phase and interpolation. Distinguish signal period, grating period, resolution and accuracy.
Separate EOM mechanisms, MZ/ring readout structures and material platforms. Compare demonstrated rates with their format, bias, BER/FEC criteria and energy boundary.
Separate bit/s, baud and Hz, then examine pulse shaping, PAM4 levels and Shannon capacity. Distinguish nominal Ethernet rates, raw coded line rates and real-link conditions.
How a voice coil creates axial force, why a carriage still needs guidance, how coil/field overlap sets useful travel, and why sustained force causes heating.
A linear motor applies force directly to the carriage with no screw in between, eliminating lead error and backlash; positioning precision is then set by the optical linear encoder and rails, so it can reach sub-micron. A coreless mover avoids detent force and is smoothest; an iron-core mover gives more force but has cogging. The cost is higher price, mover mass affecting acceleration, and a magnetic field that needs shielding.
Motion platforms classify along two dimensions — drive principle (screw, linear motor, piezo, voice coil) and axis configuration (single-axis, multi-axis, hexapod). Selection is driven by four requirements: accuracy, travel, speed, and load. Separate the five spec quantities first, then match to a type.
What do OM4, PAM4, and 800GBASE-SR8 on a module spec sheet each specify? OM is the multimode-fiber class (set by core diameter and bandwidth), PAM4 and PAM8 are modulation formats (bits per symbol), and the spec name layers on lane count and reach. This article separates the terms and gives a comparable reach table.
What do 9/125, NA, MFD, attenuation, dispersion, and bandwidth on a fiber spec sheet each specify? This article gives a parameter map and the classification …
Four focused figures explain loss, pulse spreading, single-mode conditions and MFD coupling, comparing field widths across wavelengths and products while separating specifications from teaching examples.
Three figures explain modal dispersion, OM1–OM5 OFL/EMB bandwidth and when mode-conditioning cords apply. Read specifications with wavelength, launch and link conditions.
A piezo stack directly moves a short-travel flexure stage; a walking motor accumulates longer travel. The figures distinguish low static power from mechanical self-locking, and show hysteresis, creep and actual-position feedback.
Connected serial XY stages and six-leg parallel geometry, with clear translation/rotation labels and geometric squareness/Abbe-error examples.
A screw-driven stage converts motor rotation to linear travel via a screw. Trapezoidal screws are friction-driven, have backlash, and are cheap; ball screws use ball recirculation, near-zero backlash, and higher precision. Steppers run open-loop from step angle; DC servos use encoder closed-loop, faster and tighter. Motor-axis angle, platform positioning, and workpiece tolerance are three different quantities.
Turning, milling, and drilling all cut with a pre-made edge — and the limit is not "sharpen the tool a bit." Tool-nose radius sets the ripple, edge radius sets the minimum chip, temperature makes the machine itself grow, and a silicon atom spacing is about 425,000 times smaller than a 0.1 mm end mill. Chip patterns and EUV optical surfaces are therefore not made by cutters.
From Oriental Motor steppers with ball screws to Newport DC servo and linear-motor stages: separate step angle, feedback position, minimum increment, and positioning accuracy. Converting ±0.05° to ±1.4 μm is only the motor-error component at a 10 mm lead; a 1 nm minimum increment is not a stage or workpiece tolerance.
A drawing that says 10 μm or 1 μm is asking about the finished part. ISO 230-2 positioning accuracy A describes a single axis only: an uncompensated 3-axis miller measured 20–33 μm on X; after compensation single-axis A fell to 1.3–1.7 μm while the two-axis ballbar positioning tolerance stayed around 10–13 μm. This article maps the two tolerance levels onto two published machine tests.