External cavity semiconductor laser

A laser system, comprising:

• a semiconductor laser device;
• and
• an external folded cavity including:
• a reflective surface positioned at one end of the external folded cavity,
• a mirror positioned in the external folded cavity to allow sustained propagation of light in the external folded cavity, and
• a first polarization element and a second polarization element, wherein:
• the semiconductor laser device is positioned at a cavity fold between the reflective surface and the mirror,
• the first polarization element is positioned between the reflective surface and the semiconductor laser device,
• the second polarization element is positioned between the mirror and the semiconductor laser device, and
• the first and the second polarization elements are configured to cause light that propagates from the first polarization element towards the semiconductor laser device to have an orthogonal polarization state compared to light that propagates from the second polarization element towards the semiconductor laser device.

A method for producing a substantially mode-hop-free laser system, comprising:

• providing one or more semiconductor laser devices;
• and
• forming a folded cavity external to the one or more semiconductor laser devices including:
• positioning at least one of the one or more semiconductor laser devices at a fold in the folded cavity;
• positioning at least one mirror in the folded cavity to enable sustained propagation of light within the folded cavity;
• and
• positioning at least two polarization elements in the folded external cavity, the at least two polarization elements configured to cause a polarization state of light that impinges in a first direction on each semiconductor laser device that is positioned at a corresponding fold to be orthogonal to a polarization state of light that impinges in a second direction on each semiconductor laser device that is positioned at the corresponding fold.

A laser system, comprising:

• a first semiconductor laser gain device;
• a second semiconductor laser gain device;
• and
• an external folded cavity including:
• a first mirror positioned at one end of the external folded cavity,
• an output coupler positioned at another end of the external folded cavity,
• a second mirror positioned between the first semiconductor laser gain device and the second laser gain device,
• a third mirror positioned between the second semiconductor laser gain device and the output coupler, and
• a first polarization element and a second polarization element, wherein:
• the first semiconductor laser gain device is positioned at a first cavity fold between the first mirror and the second mirror,
• the second semiconductor laser gain device is positioned at a second cavity fold between the second mirror and the third mirror,
• the first polarization element is positioned between the first mirror and the first semiconductor laser gain device,
• the second polarization element is positioned between the third mirror and the second semiconductor laser gain device, and
• the first and the second polarization elements are configured to cause light that propagates from the first polarization element towards each of the first and the second semiconductor laser gain devices to have an orthogonal polarization state compared to light that propagates from the second polarization element towards each of the first and the second semiconductor laser gain devices.