Disclosed are a current excitation type organic semiconductor laser containing a pair of electrodes, an organic laser active layer and an optical resonator structure between the pair of electrodes and a laser having an organic layer on a distributed feedback grating structure. The lasers include a continuous-wave laser, a quasi-continuous-wave laser and an electrically driven semiconductor laser diode.

An external cavity laser of a recording head includes a channel waveguide that delivers light towards a media-facing surface of the recording head. The laser includes an externally mounted part with an active region having a longitudinal axis corresponding to a light propagation direction of the channel waveguide. The externally mounted part has a reflective back facet and anti-reflective front facet. The laser includes a near-field transducer at an end of the channel waveguide proximate the media facing surface. The reflective back facet and the near-field transducer define a resonator of the external cavity laser.

Disclosed is a laser device containing a. compound represented by the following formula in a light-emitting layer, R.sup.1 and R.sup.5 each represent a substituent having a positive Hammett's σ.sub.p value, and R.sup.2 to R.sup.4, and R.sup.6 to R.sup.15 each represent a hydrogen atom or a substituent.

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A surface-emitting laser including a cladding layer, an active region, a first grating, a plurality of second gratings, a first electrode, and a second electrode is provided. The active region is disposed on the cladding layer. The first grating is disposed on the active region. The second gratings are disposed on the active region and separately distributed among the first grating. A diffraction order of the first grating is different from a diffraction order of the second gratings. The first electrode is electrically connected to the cladding layer. The second electrode covers at least the first grating.

A recording head includes an external cavity laser with an externally mounted part having an active region. The external cavity laser also includes a channel waveguide that delivers light towards a media-facing surface. A near-field transducer functions as a reflector, either alone or in combination with a Bragg grating in the channel waveguide. A reflective back facet of the externally mounted part and the reflector define a resonator of the external cavity laser.

A semiconductor laser may include an active region having a longitudinal axis, a rear facet end and a front facet end. The front facet end emitting an output beam of the semiconductor laser. The semiconductor laser may include a plurality of diffraction gratings positioned along the longitudinal axis of the active region. The plurality of diffraction gratings including a first diffraction grating positioned proximate the rear facet end of the active region and at least one additional diffraction grating positioned longitudinally between the first diffraction grating and the front facet. The first diffraction grating having a first kappa value and the at least one additional diffraction grating having at least a second kappa value, the first kappa value being greater than the second kappa value.

Semiconductors lasers are disclosed having an active region having a longitudinal axis, a first facet end, and a second facet end. The second facet end emitting the main output beam of light from of the respective semiconductor laser. The first facet end may have a low-reflection coating. The first facet end may be non-perpendicular to the longitudinal axis of the active region. The semiconductor lasers may be distributed feedback (DFB) lasers having a plurality of diffraction gratings along the longitudinal axis of the active region. The plurality of diffraction grating may include a first diffraction grating positioned proximate the first end of the active region, a second diffraction grating positioned proximate the second end of the active region, and a third diffraction grating positioned between the first diffraction grating and the second diffraction grating. The first diffraction grating may be spaced apart from the third diffraction grating along the longitudinal axis of the active region by a first distance. The second diffraction grating may be spaced apart from the third diffraction grating along the longitudinal axis of the active region by a second distance. Each of the first distance and the second distance being greater than zero.

A surface-emitting laser, which is a ridge waveguide structure, including: a substrate, a first cladding layer, an active layer, a conductive layer, a second cladding layer; the Bragg gratings is etched on the surface of the ridge waveguide; the two upper electrodes are disposed on both sides of the ridge waveguide; two grooves are formed between the ridge waveguide and each of the two upper electrodes; the first waveguide cladding layer includes one or more current confinement regions; or a buried tunnel junction is formed in the second cladding layer for limiting current. The Bragg gratings comprise two first-order gratings and one second-order grating placed between two first-order gratings.

An embodiment of the present invention provides a photodetector chip, including a substrate, a semiconductor optical amplification section, and a photodetection section. The substrate includes a surface, the photodetection section and the semiconductor optical amplification section are arranged on the substrate, and the photodetection section is located in an optical signal output direction of the semiconductor optical amplification section. The semiconductor optical amplification section amplifies and filters an input optical signal to output an amplified and filtered optical signal to the photodetection section. The photodetection section is configured to convert the amplified and filtered optical signal into an electrical signal. The semiconductor optical amplification section includes a grating, the grating includes a first grating and a second grating that are cascaded, and the first grating is a slanted grating. The first grating and the second grating are configured to filter an optical signal entering the semiconductor optical amplification section.

A semiconductor optical amplifier integrated laser includes a semiconductor laser oscillator portion that oscillates laser light having a wavelength included in a gain band and a semiconductor optical amplifier portion that amplifies laser light output from the semiconductor laser oscillator portion. The semiconductor laser oscillator portion and the semiconductor optical amplifier portion have one common p-i-n structure, the common p-i-n structure includes an active layer, a cladding layer provided apart from the active layer, and a common functional layer formed in the cladding layer, and the common functional layer includes a first portion that reflects light having a wavelength within the gain band in the semiconductor laser oscillator portion and a second portion that transmits light having a wavelength within the gain band in the semiconductor optical amplifier portion.