modellocked

Modellocked is typically a misspelling or variant of mode-locked, a technique used to generate extremely short optical pulses by forcing the longitudinal modes of a laser cavity to maintain a fixed phase relationship. When the cavity modes are locked in phase, their electric fields interfere constructively at regular intervals, producing pulses that repeat at the cavity round-trip frequency. In this sense, modellocked information or light, inaccurately spelled, refers to mode-locked operation.

Mode locking can be achieved by active or passive means. In active mode locking, an external modulator inside the cavity modulates the loss or phase at a frequency synchronized to the round-trip time, preferentially creating pulses. In passive mode locking, a saturable absorber or nonlinear optical effect inside the cavity favors high-intensity pulses, leading to self-starting pulse generation. A widely used passive mechanism is Kerr-lens mode locking, especially in solid-state lasers such as Ti:sapphire. Hybrid approaches combine elements of both methods to improve stability and performance.

Key characteristics of mode-locked lasers include pulse durations from the femtosecond to the picosecond range, repetition rates determined by the cavity length (typically tens of megahertz to several gigahertz), and broad spectral bandwidth that often approaches the uncertainty limit of the pulse duration. Achieving clean, stable pulses requires dispersion management within the cavity to balance group-velocity dispersion and nonlinearity.

Historically, mode locking was demonstrated in the mid-20th century and has become a foundational technique in ultrafast optics. Applications span frequency comb generation, ultrafast spectroscopy and time-resolved measurements, nonlinear optics, microfabrication, and biomedical imaging, making mode-locked lasers essential tools in science and industry.