Muhammad Nadeem Akram | Universitetet i Sørøst-Norge / University of South-Eastern Norway (original) (raw)
Papers by Muhammad Nadeem Akram
A dissertation submitted to the Royal Institute of Technology (KTH), Stockholm, Sweden, in partia... more A dissertation submitted to the Royal Institute of Technology (KTH), Stockholm, Sweden, in partial fulfillment for the degree of Doctor of Philosophy.
ABSTRACT Direct carrier transport measurements were performed for different InGaAsP/InGaAlAs MQW ... more ABSTRACT Direct carrier transport measurements were performed for different InGaAsP/InGaAlAs MQW test structures. Shallow InGaAlAs barrier QW showed faster carrier transport. Semi-insulating regrown FP lasers with InGaAlAs barrier QW showed improved high temperature operation, modal gain, differential modal gain and chirp.
Opt Eng, 2011
Changes have been made to this article. See the full text for a description of the changes.
16Th Iprm 2004 International Conference on Indium Phosphide and Related Materials 2004, 2004
International Topical Meeting on Microwave Photonics MWP-02, 2002
Detuned loading in directly modulated DBR lasers has been evaluated. IMD3 was measured, yielding ... more Detuned loading in directly modulated DBR lasers has been evaluated. IMD3 was measured, yielding a spurious free dynamic range of >103 dB/Hz23/ for frequencies 1-19 GHz with a top value of 116 dB/Hz23/ at 1 GHz.
Journal of Lightwave Technology
Page 1. 398 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 19, NO. 3, MARCH 2001 A New Higher Order Finite... more Page 1. 398 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 19, NO. 3, MARCH 2001 A New Higher Order Finite-Difference Approximation Scheme for the Method of Lines Hussain A. Jamid and Muhammad Nadeem Akram ...
International Symposium on Optoelectronic Technology and Application 2014: Laser and Optical Measurement Technology; and Fiber Optic Sensors, 2014
ABSTRACT We use double reversing wavefront Michelson interferometer to measure the spatial cohere... more ABSTRACT We use double reversing wavefront Michelson interferometer to measure the spatial coherence properties of high power broad area Fabry Perot edge emitting blue laser. The measurements are done at different bias current, from lasing threshold up to 1A. The laser is driven in both continuous-wave, CW and pulsed-wave modes. It is found that the magnitude of complex degree of coherence decrease when the laser is driven in pulsed mode. Among driving currents for each mode just for 700 mA bias current more uniform and rather visible interference fringes attained.
International Optical Design Conference, 2002
Optics InfoBase is the Optical Society's online library for flagship journal... more Optics InfoBase is the Optical Society's online library for flagship journals, partnered and copublished journals, and recent proceedings from OSA conferences.
Journal of Display Technology, 2012
Speckle and the compound speckle can be reduced by angle diversity. In laser projection displays,... more Speckle and the compound speckle can be reduced by angle diversity. In laser projection displays, simple, low cost and efficient speckle reduction techniques require smart optical design . Using a MEMS scanner together with a condenser lens, laser beams with different illumination angles are obtained on the diffuser surface with low speckle contrast ratio (CR). After homogenizing within a rod
Optics Express, 2014
We have recently reported a 980nm GaAs-based three terminal Pnp transistor-vertical-cavity surfac... more We have recently reported a 980nm GaAs-based three terminal Pnp transistor-vertical-cavity surface-emitting laser (TVCSEL) operating at room temperature with optical power up to 1.8mW. However, the current gain β = ΔIc/ΔIb was near zero just before lasing and became negative after the lasing threshold. The main cause of the negative current gain was found to be a gradual and position-dependent forward-biasing (saturation) of the base-collector junction with increasing bias even before lasing threshold. In this article, detailed multi-physics device simulations are performed to better understand the device physics, and find ways to avoid the premature saturation of the base-collector junction. We have optimized the thickness of the base region as well as its doping concentration and the location of the quantum wells to ensure that the T-VCSEL is in the active mode throughout its range of operation. That is, the emitter-base junction is forward biased and base-collector junction is reversed biased for sweeping the excess charges out of the base region.
31st European Conference on Optical Communications (ECOC 2005), 2005
ABSTRACT Direct carrier transport measurements were performed for different InGaAsP/InGaAlAs MQW ... more ABSTRACT Direct carrier transport measurements were performed for different InGaAsP/InGaAlAs MQW test structures. Shallow InGaAlAs barrier QW showed faster carrier transport. Semi-insulating regrown FP lasers with InGaAlAs barrier QW showed improved high temperature operation, modal gain, differential modal gain and chirp.
Speckle 2010: Optical Metrology, 2010
ABSTRACT It has been suggested to use Hadamard matrices H(M) of order M for speckle reduction in ... more ABSTRACT It has been suggested to use Hadamard matrices H(M) of order M for speckle reduction in laser based projection displays by creating a set of M two-dimensional phase masks from rows or columns of the H(M) and introducing them sequentially into the intermediate image plane of the laser projector. The speckle contrast reduction can reach M-1/2. In this paper, we have analyzed the contrast reduction. The result presents that any matrices can be used to form phase mask as long as its columns are orthogonal to each other, such as the parts of columns of Hadamard matrix. The speckle contrast reduction is determined by the number of projection resolution elements lying in single camera resolution element. To get high quality image with low speckle contrast reduction by Hadamard matrix, its order should be as high as possible. However, it is impossible to implement by vibrating diffuser with high order due to the large vibration amplitude. The motionless time-vary diffuser with Hadamard matrix phase pattern based on MEMS technology and Electro-optical effect can be a good choice.
Speckle 2012: V International Conference on Speckle Metrology, 2012
ABSTRACT We investigated the speckle contrast reduction characterization of high power broad-area... more ABSTRACT We investigated the speckle contrast reduction characterization of high power broad-area edge-emitting red and blue laser. The speckle contrast is measured with different pulse driving conditions. It can be observed from the measurement that the speckle contrast reduces with the increasing of pulse duration and pulse amplitude. The highest speckle contrast reduction that can be achieved with the red and the blue lasers is 27.9% and 10.4% respectively. The reduction of speckle contrast is due to the shift of emission wavelength and the incoherence of the laser beam at high driving current.
Semiconductor Science and Technology, 2004
... InGaAsPInGaAlAs 1.55 µm strain-compensated MQW lasers for direct modulation applications M N... more ... InGaAsPInGaAlAs 1.55 µm strain-compensated MQW lasers for direct modulation applications M Nadeem Akram, Christofer Silfvenius, Olle Kjebon and Richard Schatz ... 615 Page 3. M NadeemAkram et al inversion (or no inversion in the extreme case) to provide gain. ...
Optics Express, 2014
Despite of much effort and significant progress in recent years, speckle removal is still a chall... more Despite of much effort and significant progress in recent years, speckle removal is still a challenge for laser projection technology. In this paper, speckle reduction by dynamic deformable mirror was investigated. Time varying independent speckle patterns were generated due to the angle diversity introduced by the dynamic mirror, and these speckle patterns were averaged out by the camera or human eyes, thus reducing speckle contrast in the final image. The speckle reduction by the wavelength diversity of the lasers was also studied. Both broadband lasers and narrowband laser were used for experiment. It is experimentally shown that speckle suppression can be attained by the widening of the spectrum of the lasers. Lower speckle contrast reduction was attained by the wavelength diversity for narrowband laser compared to the broadband lasers. This method of speckle reduction is suitable in laser projectors for wide screen applications where high power laser illumination is needed.
Journal of the Optical Society of America A, 2010
Speckle suppression in projection displays with a laser light source can be achieved by imaging a... more Speckle suppression in projection displays with a laser light source can be achieved by imaging a changing diffuser with random phase cells onto the screen. Theoretical expressions for the speckle contrast in this method have been earlier obtained in the case when different realizations of the phase diffuser produced statistically independent patterns of the light field on the screen. In the present paper, these expressions are generalized in the case when different realizations of the phase diffuser produce partly correlated speckle patterns. The possible structure of a motionless changing diffuser is presented. It includes a dynamic diffractive optical element (DDOE) and a light homogenizer. The DDOE can be based on the electrically controlled spatial light modulator (SLM) with a deformable polymer layer. This type of SLM can handle high light power and, therefore, can be used in projection displays with powerful laser beams.
Optical Engineering, 2003
The design of a triple-field-of-view optical system for 3-to 5-μm infrared focal-plane arrays is ... more The design of a triple-field-of-view optical system for 3-to 5-μm infrared focal-plane arrays is described. Preliminary calculations are done to determine the first-order parameters of the narrow-, medium-, and wide-field-of-view modes. An optical configuration based on the ...
A dissertation submitted to the Royal Institute of Technology (KTH), Stockholm, Sweden, in partia... more A dissertation submitted to the Royal Institute of Technology (KTH), Stockholm, Sweden, in partial fulfillment for the degree of Doctor of Philosophy.
ABSTRACT Direct carrier transport measurements were performed for different InGaAsP/InGaAlAs MQW ... more ABSTRACT Direct carrier transport measurements were performed for different InGaAsP/InGaAlAs MQW test structures. Shallow InGaAlAs barrier QW showed faster carrier transport. Semi-insulating regrown FP lasers with InGaAlAs barrier QW showed improved high temperature operation, modal gain, differential modal gain and chirp.
Opt Eng, 2011
Changes have been made to this article. See the full text for a description of the changes.
16Th Iprm 2004 International Conference on Indium Phosphide and Related Materials 2004, 2004
International Topical Meeting on Microwave Photonics MWP-02, 2002
Detuned loading in directly modulated DBR lasers has been evaluated. IMD3 was measured, yielding ... more Detuned loading in directly modulated DBR lasers has been evaluated. IMD3 was measured, yielding a spurious free dynamic range of >103 dB/Hz23/ for frequencies 1-19 GHz with a top value of 116 dB/Hz23/ at 1 GHz.
Journal of Lightwave Technology
Page 1. 398 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 19, NO. 3, MARCH 2001 A New Higher Order Finite... more Page 1. 398 JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 19, NO. 3, MARCH 2001 A New Higher Order Finite-Difference Approximation Scheme for the Method of Lines Hussain A. Jamid and Muhammad Nadeem Akram ...
International Symposium on Optoelectronic Technology and Application 2014: Laser and Optical Measurement Technology; and Fiber Optic Sensors, 2014
ABSTRACT We use double reversing wavefront Michelson interferometer to measure the spatial cohere... more ABSTRACT We use double reversing wavefront Michelson interferometer to measure the spatial coherence properties of high power broad area Fabry Perot edge emitting blue laser. The measurements are done at different bias current, from lasing threshold up to 1A. The laser is driven in both continuous-wave, CW and pulsed-wave modes. It is found that the magnitude of complex degree of coherence decrease when the laser is driven in pulsed mode. Among driving currents for each mode just for 700 mA bias current more uniform and rather visible interference fringes attained.
International Optical Design Conference, 2002
Optics InfoBase is the Optical Society's online library for flagship journal... more Optics InfoBase is the Optical Society's online library for flagship journals, partnered and copublished journals, and recent proceedings from OSA conferences.
Journal of Display Technology, 2012
Speckle and the compound speckle can be reduced by angle diversity. In laser projection displays,... more Speckle and the compound speckle can be reduced by angle diversity. In laser projection displays, simple, low cost and efficient speckle reduction techniques require smart optical design . Using a MEMS scanner together with a condenser lens, laser beams with different illumination angles are obtained on the diffuser surface with low speckle contrast ratio (CR). After homogenizing within a rod
Optics Express, 2014
We have recently reported a 980nm GaAs-based three terminal Pnp transistor-vertical-cavity surfac... more We have recently reported a 980nm GaAs-based three terminal Pnp transistor-vertical-cavity surface-emitting laser (TVCSEL) operating at room temperature with optical power up to 1.8mW. However, the current gain β = ΔIc/ΔIb was near zero just before lasing and became negative after the lasing threshold. The main cause of the negative current gain was found to be a gradual and position-dependent forward-biasing (saturation) of the base-collector junction with increasing bias even before lasing threshold. In this article, detailed multi-physics device simulations are performed to better understand the device physics, and find ways to avoid the premature saturation of the base-collector junction. We have optimized the thickness of the base region as well as its doping concentration and the location of the quantum wells to ensure that the T-VCSEL is in the active mode throughout its range of operation. That is, the emitter-base junction is forward biased and base-collector junction is reversed biased for sweeping the excess charges out of the base region.
31st European Conference on Optical Communications (ECOC 2005), 2005
ABSTRACT Direct carrier transport measurements were performed for different InGaAsP/InGaAlAs MQW ... more ABSTRACT Direct carrier transport measurements were performed for different InGaAsP/InGaAlAs MQW test structures. Shallow InGaAlAs barrier QW showed faster carrier transport. Semi-insulating regrown FP lasers with InGaAlAs barrier QW showed improved high temperature operation, modal gain, differential modal gain and chirp.
Speckle 2010: Optical Metrology, 2010
ABSTRACT It has been suggested to use Hadamard matrices H(M) of order M for speckle reduction in ... more ABSTRACT It has been suggested to use Hadamard matrices H(M) of order M for speckle reduction in laser based projection displays by creating a set of M two-dimensional phase masks from rows or columns of the H(M) and introducing them sequentially into the intermediate image plane of the laser projector. The speckle contrast reduction can reach M-1/2. In this paper, we have analyzed the contrast reduction. The result presents that any matrices can be used to form phase mask as long as its columns are orthogonal to each other, such as the parts of columns of Hadamard matrix. The speckle contrast reduction is determined by the number of projection resolution elements lying in single camera resolution element. To get high quality image with low speckle contrast reduction by Hadamard matrix, its order should be as high as possible. However, it is impossible to implement by vibrating diffuser with high order due to the large vibration amplitude. The motionless time-vary diffuser with Hadamard matrix phase pattern based on MEMS technology and Electro-optical effect can be a good choice.
Speckle 2012: V International Conference on Speckle Metrology, 2012
ABSTRACT We investigated the speckle contrast reduction characterization of high power broad-area... more ABSTRACT We investigated the speckle contrast reduction characterization of high power broad-area edge-emitting red and blue laser. The speckle contrast is measured with different pulse driving conditions. It can be observed from the measurement that the speckle contrast reduces with the increasing of pulse duration and pulse amplitude. The highest speckle contrast reduction that can be achieved with the red and the blue lasers is 27.9% and 10.4% respectively. The reduction of speckle contrast is due to the shift of emission wavelength and the incoherence of the laser beam at high driving current.
Semiconductor Science and Technology, 2004
... InGaAsPInGaAlAs 1.55 µm strain-compensated MQW lasers for direct modulation applications M N... more ... InGaAsPInGaAlAs 1.55 µm strain-compensated MQW lasers for direct modulation applications M Nadeem Akram, Christofer Silfvenius, Olle Kjebon and Richard Schatz ... 615 Page 3. M NadeemAkram et al inversion (or no inversion in the extreme case) to provide gain. ...
Optics Express, 2014
Despite of much effort and significant progress in recent years, speckle removal is still a chall... more Despite of much effort and significant progress in recent years, speckle removal is still a challenge for laser projection technology. In this paper, speckle reduction by dynamic deformable mirror was investigated. Time varying independent speckle patterns were generated due to the angle diversity introduced by the dynamic mirror, and these speckle patterns were averaged out by the camera or human eyes, thus reducing speckle contrast in the final image. The speckle reduction by the wavelength diversity of the lasers was also studied. Both broadband lasers and narrowband laser were used for experiment. It is experimentally shown that speckle suppression can be attained by the widening of the spectrum of the lasers. Lower speckle contrast reduction was attained by the wavelength diversity for narrowband laser compared to the broadband lasers. This method of speckle reduction is suitable in laser projectors for wide screen applications where high power laser illumination is needed.
Journal of the Optical Society of America A, 2010
Speckle suppression in projection displays with a laser light source can be achieved by imaging a... more Speckle suppression in projection displays with a laser light source can be achieved by imaging a changing diffuser with random phase cells onto the screen. Theoretical expressions for the speckle contrast in this method have been earlier obtained in the case when different realizations of the phase diffuser produced statistically independent patterns of the light field on the screen. In the present paper, these expressions are generalized in the case when different realizations of the phase diffuser produce partly correlated speckle patterns. The possible structure of a motionless changing diffuser is presented. It includes a dynamic diffractive optical element (DDOE) and a light homogenizer. The DDOE can be based on the electrically controlled spatial light modulator (SLM) with a deformable polymer layer. This type of SLM can handle high light power and, therefore, can be used in projection displays with powerful laser beams.
Optical Engineering, 2003
The design of a triple-field-of-view optical system for 3-to 5-μm infrared focal-plane arrays is ... more The design of a triple-field-of-view optical system for 3-to 5-μm infrared focal-plane arrays is described. Preliminary calculations are done to determine the first-order parameters of the narrow-, medium-, and wide-field-of-view modes. An optical configuration based on the ...