Highharmonic

Highharmonic is a term used to denote high-order harmonic components in a wide range of contexts. In its broad sense, a harmonic is any integer multiple of a fundamental frequency; high harmonics are the upper end of this series, and they can carry important information about a system's dynamics, nonlinearity, and spectral content.

In music and acoustics, harmonics contribute to timbre. Instrument sounds contain a fundamental pitch accompanied by overtones at integer multiples; higher-order harmonics are often weaker but can shape brightness and edge of the sound. Instruments and players can amplify or attenuate high harmonics through materials, geometry, and playing technique. In speech and room acoustics, high harmonics influence intelligibility and resonance.

In nonlinear optics, the term high harmonic generation (HHG) is common; intense ultrafast laser pulses interacting with atoms or solids emit high‑order harmonics that extend into the extreme ultraviolet or soft X‑ray region. The process involves tunneling ionization, acceleration of electrons by the laser field, and recombination, producing attosecond-scale light bursts. HHG is used to study ultrafast dynamics and to develop bright light sources for spectroscopy and imaging.

In electronics and signal processing, high harmonics can arise from nonlinearities in amplifiers and mixers, distorting a signal. They are analyzed in distortion measurements and can be suppressed with filtering or linearization, or exploited in harmonic synthesis and testing.