Preheat oven to 350 degrees F (175 degrees C). Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente; drain. Cook spinach according to package directions; drain.
In a medium bowl, combine chicken and one jar of alfredo sauce, stir together. In a separate bowl, combine ricotta and drained, cooked spinach, and stir.
In a 9 x 13 baking dish, place one layer of lasagna noodles, edges overlapping. Pour chicken and alfredo sauce mixture over noodle layer and spread evenly. Sprinkle 1 cup of shredded mozzarella over chicken mixture. Top with another layer of noodles. Spread spinach mixture evenly over noodles. Pour 1/2 of remaining jar of alfredo sauce over spinach mixture, spread evenly. Sprinkle another cup of mozzarella over sauce, lay on the final noodle layer and top with remaining 2 cups of mozzarella and salt and pepper to taste. Bake 50 to 60 minutes, until top is brown and bubbly.