BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view showing the active layer of the laser diode of the present invention.
FIG. 2 is a schematic view showing the conduction band of the energy band according to the active layer of the laser diode of the present invention.
FIG. 3 is a three-dimensional view showing the laser diode of the present invention.
FIG. 4 is a plan view showing the laser diode of the present invention.
FIG. 5 is a plan view showing an active layer of a conventional laser diode.
FIG. 6 is a schematic view showing the conduction band of the energy band according to the conventional active layer of the laser diode.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The description taken with the drawings make the structures, features, and embodiments of the present invention apparent to the examiner how the present invention may be embodied in practice.
Referring to FIG. 1 and FIG. 2, an active layer 40 of the present invention, from bottom to top, comprises a GaInAsP quantum well layer 41, a GaInAsP quantum barrier layer 42, a GaInP layer 43, a GaInAsP quantum barrier layer 42, a GaInAsP quantum well layer 41, a GaInAsP quantum barrier layer 42, a GaInP layer 43, a GaInAsP quantum barrier layer 42, a GaInAsP quantum well layer 41, a GaInAsP quantum barrier layer 42, a GaInP layer 43, a GaInAsP quantum barrier layer 42, a GaInAsP quantum well layer 41, a GaInAsP quantum barrier layer 42, a GaInP layer 43, a GaInAsP quantum barrier layer 42, and a GaInAsP quantum well layer 41.
Referring further to FIG. 3 and FIG. 4, a laser diode A, from bottom to top, comprises a n-InP substrate 10, a n-InP cladding layer 20, an i-InGaAsP waveguide layer 30, the active layer 40, an i-InGaAsP waveguide layer 50, a P—InP cladding layer 60, and a P+InAsP layer 70.
Referring again to FIG. 1 through FIG. 4, according to the laser diode A of the present invention, the purpose of forming the i-InGaAsP waveguide layer 30 on the n-InP cladding layer 20, which is formed on the n-InP substrate 10, is to confine the optical field to the region of the quantum well layer 41 of the active layer 40 for forming the compressive-stressed quantum well layer 41. The compressive-stressed quantum well layer 41 is able to improve optical and differential gain for further reducing the critical current and increasing the speed and the optical output power. However, the quantum barrier layer 42, which has a low energy gap, cannot prevent the lateral flow of electron-hole pairs, which causes the reducing of the optical output power due to the recombination of the electron-hole pairs in the quantum barrier layer 42. In accordance with the laser diode A of the present invention, the tensile-stressed GaInP layer 43, which has a high energy gap, is formed between two non-stressed quantum barrier layers 42, which are formed between every two adjacent compressive-stressed quantum well layers 41. The utilization of the high-energy-gap, tensile-stressed GaInP layers 43 is an inventive feature of the present invention, wherein the GaInP layers 43 and the non-stressed quantum barrier layers 42 provide two functions. One of which is to prevent the recombination of the electron-hole pairs in the quantum barrier layers 42 of the laser diode A by blocking the lateral flow of the electrons for effectively reducing the hot-electron current and the current leakage, wherein the reducing of the hot-electron current causes the reducing of the critical current and the increasing of the optical output power. The other function of the non-stressed quantum barrier layers 42 is to prevent the GaInP layers 43 from compensating the compressive-stressed quantum well layers 41 so as to improve the optical and differential gain. Thereafter, the i-InGaAsP waveguide layer 50 is formed for confining the optical field. Finally, the P—InP cladding layer 60 and the P+InAsP layer 70 are formed in sequence to complete the laser diode A with the spine-shaped waveguide structure.
In accordance with the foregoing description, it is apparent that the present invention provides the advantages as follows:
- 1. the present invention indeed reduces the critical current and increases the optical output power by forming the high-energy-gap, tensile-stressed GaInP layers between the quantum barrier layers, which are formed between the quantum well layers of the active layer; and
- 2. the present invention prevents the tensile-stressed GaInP layers from compensating the compressive-stressed quantum well layers so as to improve the optical and differential gain by forming the non-stressed quantum barrier layers between the quantum well layers of the active layer.
In summary, the present invention indeed achieves the expected objects by providing the active layer of the laser diode, which is able to reduce the critical current and increase the optical output power and which is suitable for high temperature operation. Accordingly, the present invention satisfies the requirement for patentability and is therefore submitted for a patent.
While the preferred embodiment of the invention has been set forth for the purpose of disclosure, modifications of the disclosed embodiment of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments, which do not depart from the spirit and scope of the invention.
Patent Application
20070286250
