10 results about "Differential gain" patented technology

The invention relates to the technical field of lasers, in particular to a temperature self-adjusting method and device for a DFB laser with a TEC, and the method comprises the steps: collecting the temperature of the DFB laser at each moment, and the voltage and current of a TEC circuit at each moment; determining a proportional gain compensation item of the PID controller in each parameter adjustment period; analyzing the difference between the temperature change trend of the DFB laser in the local time period in each parameter adjustment period and the overall temperature change trend, and determining an integral gain compensation item of a PID controller in each parameter adjustment period; based on the fluctuation of the instantaneous frequency of the voltage and the current in the TEC circuit in each parameter adjustment period, obtaining a differential gain compensation item of a PID controller in each parameter adjustment period; and adjusting parameters of the PID controller are respectively corrected by using the proportional gain compensation item, the integral gain compensation item and the differential gain compensation item so as to adjust the temperature of the DFB laser. Therefore, the stability of temperature adjustment of the DFB laser is improved.

The application discloses a kind of high-power high-speed direct modulation quantum dot laser and preparation method thereof, N-type GaAs substrate is sent into MBE chamber to remove the surface oxidation layer, N-type GaAs contact layer is sequentially grown on the N-type GaAs substrate of surface oxidation layer removal, N-type AlGaAs restriction layer, first undoped GaAs waveguide layer, multilayer quantum dot active region, second undoped GaAs waveguide layer, P-type AlGaAs restriction layer, P-type GaAs contact layer, to obtain high-power high-speed direct modulation quantum dot laser from this. The method greatly improves the number of quantum dot layers by precisely controlling the growth conditions of quantum dots and the thickness of the spacer layer, while controlling the thickness of the quantum dot active region, thereby increasing the differential gain of quantum dots, carrier injection efficiency and greatly improving the direct modulation rate and light output power of quantum dot laser.

To provide an apparatus for determining a minimum integer number of bits required for representing non-differential gain values for compression of a HOA data frame representation.SOLUTION: When compressing the HOA data frame representation, a gain control (15, 151) is applied for each channel signal before it is perceptually encoded (16). The gain values are transferred in a differential manner as side information. However, to start decoding such a streamed compressed HOA data frame representation, an absolute gain value is needed, which should be encoded with a minimum number of bits. In order to determine such a lowest integer number of bits (β e), the HOA data frame representation (C (k)) is rendered in the spatial domain to virtual loudspeaker signals on a unit sphere, followed by a normalization of the directional signal data frame representation (C (k)). Next, the minimum integer bit number is set to β e = Γ log2 (Γ log2 ({{square root} KMAX}·O) ¬ + 1) ¬.SELECTED DRAWING: Figure 1

The invention relates to the technical field of semiconductor lasers. The number of quantum wells of the strained quantum well active region structure is limited by strain accumulation, the total thickness needs to be smaller than the critical thickness, implementation is achieved by increasing the number of the quantum wells, but the excessive number of the quantum wells can cause increase of threshold current; according to the high-speed multi-junction cascaded wafer fusion type vertical cavity surface emitting laser and the preparation method thereof, the active regions are connected in series in the same resonant cavity by using the tunnel junctions, so that the threshold carrier density is effectively reduced, the differential gain of the laser is improved, the threshold current is reduced, and the performance of the laser is improved. And the output power and the small signal modulation bandwidth of the laser are remarkably improved while the resistance and the absorption loss are not multiplied.

When compressing an HOA data frame representation, a gain control (15, 151) is applied for each channel signal before it is perceptually encoded (16). The gain values are transferred in a differential manner as side information. However, for starting decoding of such streamed compressed HOA data frame representation absolute gain values are required, which should be coded with a minimum number of bits. For determining such lowest integer number (βe) of bits the HOA data frame representation (C(k)) is rendered in spatial domain to virtual loudspeaker signals lying on a unit sphere, followed by normalisation of the HOA data frame representation (C(k)). Then the lowest integer number of bits is set to βe=log2log2KMAX⋅O+1 .

This invention discloses a small array structure for a vertical-cavity surface-emitting laser (VCSEL), comprising, from bottom to top, a negative electrode layer, an N-type GaAs substrate, a lower N-type diode-controlled laser (DBR), an active region layer, an electron blocking layer, an aperture oxide confinement layer, an upper P-type DBR, a small array structure, and a polymer lens layer. The active region layer includes two sets of chirped quantum wells, each with a narrow-domain steep-change SCH layer on both sides. The two sets of chirped quantum wells are connected by a tunnel junction to form a double-junction structure. The small array structure includes multiple independent small-aperture VCSEL units. This invention enhances thermal stability and expands the device's wide-temperature-range output capability through four sets of quantum wells; it significantly improves differential gain and optical gain bandwidth by cascading multiple quantum wells through the double-junction structure; it broadens the gain spectrum, enhances mode stability, and expands the gain control range through chirped quantum wells; and it achieves single-mode high-power output through the small array structure, resolving the performance contradiction between penetration and accuracy.

This invention relates to the field of semiconductor laser technology, specifically to a single-mode semiconductor laser with a superlattice structure and its fabrication method. A single-mode semiconductor laser with a superlattice structure is characterized by comprising, from bottom to top, an N-type electrode, an N-GaAs substrate, an N-GaAs contact layer, an N-AlGaInP confinement layer, an N-AlGaInP waveguide layer, a multiple quantum well layer, a superlattice structure, a P-AlGaAs waveguide layer, a P-AlGaInP confinement layer, a P-GaAs contact layer, a SiO2 layer, and a P-type electrode. This invention improves the device's differential gain and high-temperature stability through the superlattice structure, suppresses spatial hole burning by setting multiple phase-shift gratings along the cavity length, and achieves single-transverse mode, near-diffraction-limited beam output in conjunction with a narrow ridge waveguide. The device fabricated by this invention exhibits excellent power stability after 3000 hours of aging testing, has a high single-mode yield, and is suitable for laser sensing, fiber coupling, and other applications.

According to the gallium nitride-based semiconductor laser with the gradually-changed longitudinal phonon rate waveguide layer, a fitting curve of In ion strength distribution or In atom concentration distribution of an upper waveguide layer and a lower waveguide layer is tested through an SIMS, a fitting curve of the longitudinal phonon rate meets any function distribution of Allometric2, Allometric1, BiPhasic and FreundichEXT, and the longitudinal phonon rate of the upper waveguide layer and the lower waveguide layer meets any function distribution of the Allometric2, the Allometric1, the BiPhasic and the FreundichEXT. The upper waveguide layer, the lower waveguide layer and the longitudinal (perpendicular to a quantum well surface) phonon group velocity and phonon energy gradient are regulated and controlled, directional management of phonon transportation and scattering is achieved, smooth transition of phonon group velocity is achieved through the gradually-changed longitudinal phonon velocity structure of the upper waveguide layer and the lower waveguide layer, interface reflection and back scattering are reduced, and the quantum efficiency is improved. And thirdly, mismatch between phonon energy and quantum well energy level difference is reduced, resonance scattering is reduced, the carrier relaxation rate is reduced, differential gain is improved, accumulation of high-energy phonons in a waveguide layer and a quantum well is inhibited, and heat reversal current is improved.

The application provides a vertical cavity surface emitting laser chip, which comprises a substrate and, from bottom to top, a buffer layer, an N-type DBR layer, a first SCH layer, a second SCH layer, a quantum well structure layer, a third SCH layer, an oxidation structure layer, a P-type DBR layer and a P-type contact layer, wherein a tunneling layer is prepared between the first SCH layer and the quantum well structure layer, the band gap of the tunneling layer is larger than that of the quantum well structure layer, carriers are transmitted to the tunneling layer through the N-type DBR layer and the first SCH layer, and then are injected into the quantum well structure layer in a tunneling mode to be transmitted in a tunneling mode. The application increases the tunneling layer between the SCH layer and the quantum well structure layer, and optimizes the thickness of the barrier layer in the quantum well structure layer, so that the carriers are injected into the quantum well structure layer in a tunneling mode and are transmitted in a tunneling mode between the quantum well layer and the barrier layer, thereby improving the carrier transmission effect and the hot carrier effect and increasing the differential gain, and finally realizing high modulation bandwidth.

A fiber amplifier is provided, including a pump laser (202), a pump and signal combiner (203), and a few-mode doped fiber (204). The pump laser (202) is configured to output pump light. The pump and signal combiner (203) is configured to couple input few-mode signal light and the pump light into the few-mode doped fiber (204). Refractive indexes of a fiber core of the few-mode doped fiber (204) are distributed to be gradient along a radial direction of a cross section, the fiber core is etched with periodic gratings along an axial direction, and periods of the gratings satisfy a phase matching condition. The fiber amplifier achieves strong coupling and co-amplification between optical signal modes, thereby reducing a differential gain between mode groups.