page_title: Superluminescent diode
section_title: Dependence of power on current
hierarchical_section_title: Superluminescent diode / Main characteristics / Dependence of power on current
context_page_description: A superluminescent diode is an edge-emitting semiconductor light source based on superluminescence. It combines the high power and brightness of laser diodes with the low coherence of conventional light-emitting diodes. Its emission band is 5–700 nm wide.
context_section_description: The total optical power emitted by an SLED depends on the drive current. Unlike laser diodes, the output intensity does not exhibit a sharp threshold but it gradually increases with current. A soft knee in the power vs. current curve defines a transition between a regime dominated by spontaneous emission (typical for surface emitting LEDs) and one that is dominated by amplified spontaneous emission (i.e. superluminescence). Even if the output power is based on spontaneous emission it has to be noted that the amplification mechanism affects the polarization state of the emitted radiation in a way which is related to the SLED structure and on the operating conditions.
  The maximum value of the current that allows a safe operation of the device depends on the model and ranges between 70 mA (for low power SLED) and 500 mA for the most powerful devices.
caption: Typical dependence of the fibre-coupled optical power vs. injected current for a SLED module with a central wavelength of 1550 nm, a 3-dB bandwidth of 60 nm and a typical output power of 1.5 mW  at 20°C.