Local density of optical states calculated by the mode spectrum in stratified media

The local density of optical states(LDOS)is an important physical concept,which can characterize the spontaneous emission of microcavities.In order to calculate the LDOS,the relationship between the mode spectrum and the LDOS is established.Then,based on the transfer matrix method and the effective resonator model,the leaky loss of the leaky mode and the mode spectrum in the one-dimensional photonic bandgap crystal waveguide are calculated,results of which indicate that the mode spectrum can characterize the leaky loss of the leaky mode.At last,the density of optical states(DOS),and the LDOS in each layer are calculated.The partial DOS and the partial LDOS in the quantum well,related to the fundamental leaky mode,can be used to find out the optimal location of the quantum well in the defect layer to couple more useful photons into the lasing mode for lasers.

Experimental Protection of the Spin Coherence of a Molecular Qubit Exceeding a Millisecond

Molecular qubits are promising as they can benefit from tailoring and versatile design of chemistry.It is essential to reduce the decoherence of molecular qubits caused by their interactions with the environment.Herein the dynamical decoupling(DD)technique is utilized to combat such decoherence.The coherence time for a transitionmetal complex(PPh_(4))_(2)[Cu(mnt)_(2)]is prolonged from 6.8μs to 1.4 ms.The ratio of the coherence time and the length ofπ/2 pulse,defined as the single qubit figure of merit(QM),reaches 1.4×10^(5),which is 40 times greater than what previously reported for this molecule.Our results show that molecular qubits,with milliseconds coherence time,are promising candidates for quantum information processing.

Improvement on the topological localized interface enabled by chiral symmetry

Zero-energy topological states,which are protected by chiral symmetry against certain perturbations topologically,localize at interfaces between trivial and non-trivial phases in the Su–Schrieffer–Heeger(SSH)chain model.Here,we propose and demonstrate a method to manipulate chiral symmetry itself to improve the localized interfaces and enlarge the mode volume of topological states in the SSH model,thus optimizing the lasing performance of localized interfaces.As multiple defects corresponding to off-diagonal perturbations in an eigenmatrix are introduced,the topological state expands and extends to extra defects at the topological interface without breaking chiral symmetry.We apply the proposed method in electrical pumping semiconductor laser arrays to verify our theoretical prediction and optimize the output characteristics of the devices.The measured results of the proposed multi-defect SSH laser array show that the output power has been increased by 27%,and the series resistance and far-field divergence have been reduced by half compared to the traditional SSH laser array,establishing a high-performance light source for integrated silicon photonics,infrared light detection and ranging,and so on.Our work demonstrates that the proposed method is capable of improving topological localized interfaces and redistributing zero-energy topological states.Furthermore,our method can be applied to other platforms and inspire optimizations of more devices in broader areas.