Emitting 1530 nm light on Silicon wafer is very useful because 1530nm is an important band in optical fiber communication. We explore a new way of light emission at 1530 nm. We demonstrate a simple and non-expensive process to form light-emitting layer. It can be deposited on silicon wafers. The properties of samples can be varied through controlling the composition. The emission efficiency can be further improved by introducing P2O5 and Yb2O3 nanoparticles into the solution. This emitting layer is able to show the signals only within several millimeters due to surface effect of nanoparticles, enabling the higher concentration of Er3+. The optical gain at 1530nm is measured using variable stripe length method. The gain coefficient can be as large as 18 cm-1.
The effects of phonon bottleneck effect on the performance of QD laser devices are studied using the rate equation model. Due to phonon bottleneck effect, simultaneous laser oscillations of ground state and excited state can occur. By comparing experimental data and theoretical prediction, the estimated value of intra-dot relaxation time is more than 100ps.
A new-type tunable high power wavelength tunable ASE light source is fabricated. The device length is 1960μm. The waveguide is 100μm wide and tilted at 6° from the facet normal. Without external feedback, this device can provide 1.4Watt ASE light per facet at 12Amp injection current. The emitted spectrum has 20nm FWHM. The far field has narrow divergence angle and the near field is smooth without filamentation. When external feedback is applied, the slope efficiency is increased from 0.15W/Amp to 0.2W/Amp. Only 6Amp injection current is required to reach 1.06Watt output. Feedback from a grating can be used to control the emission wavelength and improve the beam quality.
Laser mode competition is a well-known phenomenon in a multi-mode laser system. The competition between different lasing modes is considered inevitable in all kinds of lasers. However, our experiments show that laser mode anti-competition can be observed in lasers that combine either quantum dots (QD) of different sizes or quantum wells of different composition and width. Here we report the anti-competition experiment from QD lasers. The QD structure is grown on a GaAs substrate. Two types of QD layers for 1.24μm emission and 1.28μm emission are grown alternatively in the active layer. The anti-competition behavior is observed in an external cavity laser controlled by the grating, oscillating at two different wavelengths. Experimental results show that when short-wavelength light intensity increases, long-wavelength light intensity will also increase. This is the anti-competition behavior. Nonetheless, when short-wavelength light intensity is above a certain level, long-wavelength light intensity decreases. It means that the laser behavior changes to the usual competition situation at the large intensity.
The wavelength of the designed two-section laser diode can be modulated by direct current modulation. The modulation speed of intensity of each wavelength is 1.5 times faster than the speed of a direct modulated single section laser. The modulation depth of output intensity can be 20dB.
Dual-wavelength semiconductor laser with wavelength separation as large as 203 nm is reported. With the short-wavelength mode located in 1345.4 nm and the long-wavelength mode in 1548.6 nm, the operation region of the laser system covers both the medium-wave band (1300 nm region) and long-wave band (1500 nm region) in optical communication. Random selection of oscillating wavelength position between 1345.4 nm and 1548.6 nm is also possible with fixed wavelength separation. This broadband laser system provides an opportunity for all-optical switching between the medium-wave band and long-wave band in optical communication.
KEYWORDS: Waveguides, Semiconductor lasers, High power lasers, Near field, Amplifiers, Near field optics, Diodes, Diffraction gratings, Optical amplifiers, Semiconducting wafers
High power and good beam quality are desired for semiconductor lasers in many applications. We propose a new type of broad area laser diodes that is capable of emitting good beam quality, high power and broadband tuning. The new type of laser diodes is fabricated with a broad-area waveguide that is oriented at an angle from the facet normal. This device does not require the DFB structure, so the fabrication is much simpler. The L-I curves, spectra, near-field patterns and far-field patterns of the angled broad-area waveguide laser diode are measured. The direction of the far field pattern along the facet normal for the device operated above the threshold current indicates that the light path is not along the waveguide direction. As the laser diode is inserted in a grating-loaded external cavity, it is tunable from 1280nm to 1315nm with output power up to 1.4 watt at 8Amp. The beam quality is good and the near field has negligible filamentation.
We introduce a new fabricating technique that forms a light emitting layer on silicon wafer. This emitting layer could emit light at 1530nm. We mix the Er2O3 nanoparticles with spin-on glass, then deposit this mixed solution onto silicon wafer. It emits 1530nm light because Er2O3 nanoparticles release Er3+ into glass at high temperature. The manufacturing process is very simple and low cost. We also add P2O5, Si, Al, and Ag nanoparticles in order to modify the physical characteristics and light emission efficiency.
KEYWORDS: Waveguides, Semiconductor lasers, Near field, Near field optics, High power lasers, Light wave propagation, Waveguide lasers, Amplifiers, Refractive index, Diodes
High-power semiconductor lasers with good beam quality are important for many applications. Angled broad-area waveguide structure could increase the output power and the beam quality is maintained at good quality. In this paper, we report the in-depth investigation on the geometrical factors that influence the performance of angled broad-area semiconductor lasers. The angled broad-area laser diodes are based on InGaAsP/InP materials. The waveguide is oriented at an angle from the normal of the cleaved facets. Our investigation shows that the waveguide width, the device length, and the tilted angle have to follow a certain relation in order to have the light propagate along a zigzag path inside the broad-area waveguide. When such a mode oscillates, the output light emits along the normal of the cleaved facet, showing no filamentation. Over 1 W of output power can be obtained with a good beam quality. Our investigation also discovers that devices with 100μm waveguide width perform better than devices with 50μm waveguide width.
KEYWORDS: Waveguides, Semiconductor lasers, Near field, Fabry–Perot interferometers, Broad area laser diodes, Diffraction gratings, Laser damage threshold, YAG lasers, Reactive ion etching, Near field optics
A new type of laser diodes with good beam quality is introduced. The far-field divergence angle can be close to diffraction-limited value. In the new design, the direction of the waveguide on a broad area Fabry-Perot laser diode is tilted at an angle from the facet normal. This design is called “angled broad area laser diode”. In this tilted waveguide device, filamentation is not observed. The far-field divergence angle is generally within 5 times the diffraction-limited
value. This tilted broad area laser is advantageous over the angled grating DFB laser because the difficulty of matching the grating period with peak gain wavelength is avoided.
Nonidentical multiple quantum wells (MQWs) had been widely used for broadening the emission or gain bandwidth of semiconductor optical amplifiers (SOAs). However, the carrier distribution among the MQWs is not uniform, leading to nonuniform gain contributed from different QWs. Thus using nonidentical MQWs for broadband purpose is not intuitively straightforward. Several factors need to be carefully considered. Those factors include the QW sequence, electron/hole transport time across the separate confinement hetero-structure, as well as carrier capture time. In this work, we will discuss the design of MQWs for broadband SOAs. With properly designed nonidentical MQWs, the emission bandwidth could be nearly 400 nm. Also, the tuning range of semiconductor lasers could be extended to be over 200 nm.
Novel bi-directional propagation is observed in a shallow-etched bending ridge waveguide. The lasing light propagates in two different paths, straight way and bending way. The far-field pattern is quite different before and after the lasing condition is reached. Emission spectra of light emitted from two facets are also different. This is because the bidirectional guided effect of lasing mode occurs.
A broadly tunable range of 200 nm is achieved in external cavity semiconductor laser using a Fabry-Perot laser diode as an amplifier. The broadband tuning is possible due to two reasons. First, the gain bandwidth is broadened using proper design of nonidentical quantum-well structure. Second, carriers distribute over a broad bandwidth, leading to the reduction of gain over a narrow bandwidth. Thus self-oscillation of uncoated Fabry-Perot laser didoes is suppressed, but there is still gain for external-cavity configuration. A tuning range covering from 1340nm to 1540nm is then achieved.
Superluminescent diodes with broad emission bandwidth characteristics and the mechanism of carrier distribution in the active layer are explored. Asymmetric active layer structure is used for the broadband purpose. Using InP substrate with five 60Å InGaAsP quantum wells and two 150Å InGaAs quantum wells, we get a very broad emission spectrum. The spectral width is nearly 400 nm, almost covering the range from 1250nm to 1650nm.
Extremely broadband tunability of semiconductor lasers is achieved. The tuning range covers from 1300 nm to 1540 nm using nonidentical multiple quantum wells (MQWs) in the gain media. The broadband gain medium has two In0.53Ga0.47As quantum wells (Qws) near the n-cladding layer and three In0.67Ga0.33As0.72P0.28 Qws near the p-cladding layer. The sequence of the MQWs is also found to be very influential on the tuning range. For the sequence opposite to the above one, the tuning range is only from 1290 nm to 1450 nm. The reason is because the well sequence influences the carrier distribution. The broadband tunability is possible only when the QW structure could have a better uniformity of carrier distribution.
Semiconductor lasers with InGaAsP/InP nonidentical multiple quantum wells (MQWs) for optical communication are experimented to show the improved temperature characteristics. With proper layout of the nonidentical MQWs, the characteristic temperature of the laser diodes is increased. Also, the differential quantum efficiency increases to around 40% for the temperature increasing from 30 degree(s)C to 40 degree(s)C and approximately remains at this value for temperature above 40 degree(s)C. The reason is attributed to the carrier redistribution in the nonidentical MQWs as temperature increases. The change in temperature causes certain QWs to have increased carriers. Therefore their corresponding gain increases to overcome other effects that degrade temperature characteristics. With proper design of nonidentical MQWs, significant improvement on temperature characteristics of semiconductor lasers is possible.
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