Browsing by Subject "Diode lasers"

Now showing 1 - 2 of 2

Open Access
Facet cooling in high-power InGaAs/AlGaAs lasers
(Institute of Electrical and Electronics Engineers Inc., 2019) Arslan, Seval; Gündoğdu, Sinan; Demir, Abdullah; Aydınlı, A.
Several factors limit the reliable output power of a semiconductor laser under CW operation, such as carrier leakage, thermal effects, and catastrophic optical mirror damage (COMD). Ever higher operating powers may be possible if the COMD can be avoided. Despite exotic facet engineering and progress in non-absorbing mirrors, the temperature rise at the facets puts a strain on the long-term reliability of these diodes. Although thermoelectrically isolating the heat source away from the facets with non-injected windows helps lower the facet temperature, data suggests the farther the heat source is from the facets, the lower the temperature. In this letter, we show that longer non-injected sections lead to cooler windows and biasing this section to transparency eliminates the optical loss. We report on the facet temperature reduction that reaches below the bulk temperature in high power InGaAs/AlGaAs lasers under QCW operation with electrically isolated and biased windows. Acting as transparent optical interconnects, biased sections connect the active cavity to the facets. This approach can be applied to a wide range of semiconductor lasers to improve device reliability as well as enabling the monolithic integration of lasers in photonic integrated circuits.
Open Access
Ultrafast burst-mode fiber lasers: source development and material processing
(IEEE, 2015) İlday, F. Ömer
High-precision processing of materials with ultrafast laser pulses is drawing increasing attention as laser sources are finally catching up with industry requirements. In particular, very rapid progress has been achieved in ultrafast fiber lasers, which are popular as a result of their highly repeatable, environmentally robust performance, compact size and possibility to reach high average powers. Meanwhile, our understanding of the rich physics of ultrafast laser-material interaction remains incomplete, wherein lies new opportunities. A particularly exciting possibility concerns the use of groups of pulses, which are extremely closed in time. This changes the interaction physics drastically: A unqualified increase in laser repetition rate would result in severe heat accumulation and other undesirable effects. The average power can be kept at a desirable level by operating the laser in the so-called burst mode, whereby each burst contains a number of closely spaced pulses, benefiting from accumulative effects, while the bursts are repeated at much lower repetition rate. Under the right conditions, including keeping average power low enough to prevent excessive heat accumulation, relatively low peak powers for which plasma shielding and similar effects are reduced, ultrafast burst mode can lead to an order-of-magnitude increases in processing speed compared to uniform repetition rate operation of an otherwise identical laser source.