Photonic devices and methods

A method for operating a photonic device comprising a waveguide structure having a junction element with at least two input waveguide channels converging at the junction element, a saturable absorber positioned at, within, or immediately adjacent to the junction element, and no waveguide, port, or optical coupling structure configured to introduce a pump or auxiliary optical beam, the method comprising:

• providing respective logical input optical signals to the at least two input waveguide channels such that the logical input optical signals propagate toward and converge at the junction element;
• interacting, at the junction element, the saturable absorber interacting with said logical input optical signals for generating at least one output optical signal, said at least one output optical signal being a selected function of said logical input optical signals, wherein
• said saturable absorber interacts with said logical input optical signals in accordance with a first attenuation rate for optical signals of a first intensity range, and with a second attenuation rate for optical signals of a second intensity range, where the second intensity range is higher than the first intensity range;
• and
• total optical intensity impinging on the saturable absorber is derived solely from the logical input optical signals arriving at the junction through the at least two input waveguide channels, such that the saturable absorber operates without any pump or auxiliary optical beam;
• and
• receiving said at least one output optical signal from at least one respective output waveguide channel extending away from the junction element.

A photonic device comprising:

• a waveguide structure comprising a junction element having at least two input waveguide channels that converge at the junction element and at least one output waveguide channel extending away from the junction element, each input waveguide channel guiding a respective logical input optical signal toward the junction element;
• and
• a nonlinear optical element comprising a reverse saturable absorber (RSA) positioned at, within or immediately adjacent to the junction element, the RSA being configured to interact with guided-mode optical energy carried by the logical input signal as the logical input optical signals converge at the junction element;
• wherein the RSA exhibits increasing attenuation with increasing intensity of the logical input optical signals within a selected operating range;
• and
• wherein placement of the RSA at, within, or immediately adjacent to the junction element causes the RSA to interact with a combined modal field distribution of the at least two logical input optical signals at the junction element so as to generate, in the output waveguide channel, an output optical signal that is a selected function of the input optical signals.